Recommended Practice
Proposed RP 171 (T)
VMRS 034-001
High-Performance Coatings for Forward
Lighting On Commercial Trucks
PREFACE
The following Recommended Practice is subject to
the Disclaimer at the front of TMC’s Recommended
Engineering Practices Manual. Users are urged to
read the Disclaimer before considering adoption of
any portion of this Recommended Practice.
Eventually, glass sealed beam headlamps were
replaced with plastic sealed beam lamp assemblies.
These plastic assemblies offered many benefits, such
as reduced weight and greater impact resistance. Being sealed beam lamps, however, the entire assembly
needed to be replaced when the lamp failed.
PURPOSE AND SCOPE
The purpose of this Recommended Practice (RP) is
to provide guidelines for specifying forward lighting
coating systems for plastic headlamps that not only
meet applicable federal requirements but also provide the basis for more robust coating performance
in on-highway applications.
In 1985, a new forward lighting technology emerged
called “aerodynamic headlamps” and the National
Highway Traffic Safety Administration (NHTSA) developed new specifications for these devices.
This RP defines performance requirements for
forward lighting high-performance coatings used
on commercial trucks. It augments, with specific
requirements, the standards depicted in various SAE
and TMC Recommended Practices covering the
general design and performance of forward lighting
coating systems.
This RP covers coatings used on headlamps, fog
lamps and driving lamps (collectively referred to as
forward lighting) using plastic lenses. It supplements,
but does not replace Federal Motor Vehicle Safety
Standards (FMVSS), Federal Motor Carrier Safety
Regulations (FMCSR) and other applicable state
and local vehicle regulations. Use of this RP does
not in any way relieve manufacturers or equipment
users of the necessity of complying with applicable
federal, state and/or local regulations.
INTRODUCTION
Headlamps, fog lamps and driving lamps were for
many years made of glass lenses. The light sources
were incandescent or halogen bulbs which had
relatively short lives and when these sealed beam
devices failed an entirely new lamp assembly was
installed to replace the failed device. Accordingly,
the replacement light source included new lenses
and bulbs.
© 2013—TMC/ATA
Aerodynamic headlamps have several advantages
over sealed beam technology:
• aerodynamic styling is integrated into the style
of the vehicle,
• the light source is a replaceable bulb module,
and;
• the headlamp can potentially last for the life
of the vehicle.
Unfortunately, material and coating specifications for
aerodynamic headlamps were originally driven by
the automotive industry, which did not consider the
requirements of the commercial vehicle market. By
2000, aerodynamic headlamps began appearing on
commercial vehicles. New designs looked great but
the coatings used were not robust enough to endure
commerical vehicle applications.
New headlamp designs embody light emitting diode (LED) Light sources that have an even greater
potential of lasting the life of the truck. Therefore,
efforts must be taken to improve performance of
the coatings used on headlamps and other forward
lighting devices.
RECOMMENDED SPECIFICATIONS
TMC believes the following recommendations will help
equipment purchasers specify a more robust coating
for their vehicles’ forward lighting devices.
Proposed RP 171 (T) Ballot Version—
Issued x/xxxx
A. Lens Material
Clear polycarbonate is the plastic of choice for nearly
all forward lighting devices in the commercial vehicle
market.
B. Headlamp Coating Options
There are two headlamp coating options available:
single-component UV curable coatings, and twocomponent thermally cured silicone hard coatings.
• Single-Component UV Curable Coatings—
These are the coatings that are used on most
passenger car and light truck headlamps.
These coatings, when properly applied, meet
the minimum legal performance requirements
for haze, durability, weatherability, chemical
resistance and resistance to yellowing. Single
component coatings are generally an acrylicbased coating which is quickly cured under a
ultraviolet (UV) light. Typical application times
for this process are about 10 minutes for the
entire process. Many of these coatings are
listed in the Automotive Manufacturers Equipment Compliance Agency (AMECA) listing of
approved materials.
• Two-Component Thermally Cured Silicone
Hard Coatings—This coating process consists
of a primer applied to the polycarbonate lens,
then baked, followed by a silicone topcoat
layer and baked again. This coating is applied
using a more complex process and has many
superior performance benefits when compared
to single component coatings, such as:
- abrasion and mar resistance,
- improved weatherability,
- extended service life,
- excellent resistance to micro-cracking,
- excellent ultraviolet radiation protection,
- improved thermal, solvent and chemical
resistance.
In some applications, this coating reportedly
holds up better than the body paint used
next to the coated part. These coatings are
also featured in AMECA’s listing of approved
materials.
Fleets that operate vehicles in typical on-highway
applications should consider spec’ing the two-component, thermally cured silicone hard coat system.
This will help ensure their vehicles’ headlamps will
last the typical service life expected by the vehicle’s
first owner. Because the appearance of both of these
headlamp coating systems is clear, it is important that
© 2013—TMC/ATA
the purchaser obtains a certification from the vehicle
manufacturer that selected hard coat of choice has
been applied to the headlamps.
GLOSSARY OF TERMS
Coating—Material applied to surface of the lens to
improve some aspect of performance.
Coated Materials—Finished component which
has a coating applied to its surface to impart some
protective properties.
Cracking—A separation of adjacent sections of a
plastic material with penetration into the specimen.
Crazing—a network of apparent fine cracks on or
beneath the surface of materials.
Delamination—A separation of the layers of a material including coatings.
Hard Coat – Coating that provides additional resistance to abrasion or scratching which may be cured
either thermally or by UV radiation. May contribute to
long-term durability of a material. The curing process
employed is important determining factor of coating
performance.
Haze—The cloudy or turbid appearance of an otherwise transparent specimen caused by light scattered
from within the specimen or from its surface.
High-Intensity Discharge (HID) Lamp—Produces
light through the use of a stabilized arc. HID Lamps can
produce significant UV radiation which may require
special materials. See SAE J1647, Plastic Materials
and Coatings for Use In or On Optical Parts Such as
Lenses and Reflectors of High-Intensity Discharge
Forward Lighting Devices Used in Motor Vehicles.
Substrate—Base material to which all other performance enhancing materials are added.
UV-Protective Coat—Coating designed to provide
additional protection from the sun’s radiation, particularly those wavelengths in the UV bandwidth.
Often used on polycarbonate substrates to improve
weathering performance. Polycarbonates must be
coated for use in headlamps.
UV Radiation—Short wavelength, high energy radiation emitted by the sun or other object (HID or LED
lamp). Wave lengths between 10 and 380 nm.
Proposed RP 171 (T) Ballot Version—
REFERENCES
Federal Motor Vehicle Safety Standard (FMVSS)
No. 108; Lamps, reflective devices, and associated equipment. http://www.fmcsa.dot.gov/rulesregulations/administration/fmcsr/fmcsrruletext.
aspx?reg=r49CFR571.108
Canadian Motor Vehicle Safety Standard (CMVSS)
No. 108; Lighting System and Retroflective Devices.
http://www.tc.gc.ca/eng/roadsafety/tp-tp13136tr108-846.htm
Automotive Manufacturers Equipment Compliance
Agency (AMECA) Listing. Automotive Manufacturers
Equipment Compliance Agency, Inc., 1025 Connecticut Avenue, NW Suite #1012, Washington DC 20036 .
http://www.ameca.org/wp-content/uploads/2012/02/
AMECA-March-2012-List-of-Acceptable-Plastics-forOptical-Lenses-and-Reflex-Reflectors.pdf
© 2013—TMC/ATA
Proposed RP 171 (T) Ballot Version—
Recommended Practice
Proposed RP 172 (T)
VMRS 034-001
Recommended Cleaning and Maintenance
of Headlamps for Commercial Vehicles
PREFACE
The following Recommended Practice is subject to
the Disclaimer at the front of TMC’s Recommended
Maintenance Practices Manual. Users are urged to
read the Disclaimer before considering adoption of
any portion of this Recommended Practice.
PURPOSE AND SCOPE
This Recommended Practice (RP) provides guidelines for the cleaning, maintenance and restoration of
headlamp systems used on commercial vehicles. It
defines the expected performance requirements and
augments, with specific requirements, the standards
depicted in the SAE and TMC Recommended Practices covering the general maintenance of forward
lighting coating systems. Use of this RP does not in
any way relieve manufacturers or equipment users
of the necessity of complying with applicable federal,
state and/or local regulations.
BACKGROUND
Headlamp assemblies were much simpler in the early
days of trucking when there was only one type of unit
used—a glass seven-inch round sealed beam lamp
assembly. As time went on, these were replaced by
5"x7" inch rectangular beam and rectangular quad
beam assemblies but the material was always glass
and simple to clean with just about anything. If a lens
did get stained, before too long the filament would
fail and the unit would be replaced with a new lamp
assembly.
By 2000, aerodynamic headlamps began appearing
on commercial vehicles, and with them came new
maintenance concerns. Glass sealed beams were
replaced by polycarbonate lamp assemblies which
needed a coating to hold up to the chemicals, abrasion, washing and sun.
The coating used on headlamps is often a single-coat,
ultraviolet (UV) cured, clear acrylic material. This is
acceptable for automotive applications, but may not
be as suitable for commercial vehicle applications.
© 2013—TMC/ATA
Additionally, polycarbonate is a durable material
with great impact strength but it can be attacked by
hydrocarbon solvents. These solvent can reduce the
service life of the headlamp assembly, causing hazing
and micro-cracks in the lamps assembly.
MAINTENANCE RECOMMENDATIONS
Accordingly, TMC has developed the following cleaning, maintenance and restoration guidelines for headlamps used in commercial vehicle applications.
A. Procedure For Cleaning
Cleaning can be best achieved using a mild warm
soapy water with a soft cloth on the face of the lens.
See Table 1 for a list of solvents and cleaners that
are compatible with polycarbonate.
Using of solvents that are not compatible with polycarbonate will result in the softening, crazing, and/or
cracking of the plastic part. This is especially true
of polycarbonate lamps and mounting bases which
may be under stress in their normal applications.
See Table 2 for a list of solvents and cleaners that
are not compatible with polycarbonate.
TABLE 1:
SOLVENTS/CLEANERS THAT ARE
COMPATIBLE WITH POLYCARBONATE
Mild soap and water
Mineral Spirits
Hexane
VM and P Naphtha
Varsol No. 2
#1 and #3 denatured alcohol
Freon TF and TE-35
Ethanol
10% Sol Ban Ami®
Dirtex®
2% Sol. Reg. Joy
Heptane
White Kerosene
Methyl, isopropyl and isobutyl alcohols
Lacryl® PCL-2035 polycarbonate cleaner
Petroleum Ether/65°C boiling point
Proposed RP 172 (T) Ballot Version—
Issued x/xxxx
TABLE 2:
SOLVENTS/CLEANERS THAT ARE NOT
COMPATIBLE WITH POLYCARBONATE
Texine-8006, 8129, 8758
Liquid Cleaner - 8211
Agitene®>
AJAX®
All liquid detergents
Pink Lux® (phosphate free)
Diversol®
Lemon Joy® (phosphate free)
Kleenol Plastics
Lestoil®
Stanisol Naphtha®
Oils
Mean Green®
Simple Green®
B. Procedure For Restoration
If haze begins to appear on the surface of an aerodynamic headlamp, or if the headlamp begins losing its ability to illuminate sufficiently, chances are
some improvement can be gained from restoration
treatment.
Headlamps are precision optical instruments. The
appearance of haze often diffuses the headlamp
beam into areas other than what was intended in
the original optical design. Heavily diffused or hazed
lamps can often provide excessive glare to oncoming drivers and at the same time create illumination
issues for the vehicle being operated.
Working to restore a headlamp or to improve the
beam requires a multi-step approach that starts
with the simplest method and continues to get more
complex as required:
1. The first step is to wash the headlamp with
some soapy warm water and make an assessment of the condition of the headlamps.
2. If it appears that the haze does not improve
significantly, the next step is to examine the
outside surface of the lens to determine if the
coating has started to break down. Has the
surface finish begun to lose its luster or is the
coating is breaking down? If so, consider using
a headlamp restoration kit.
Headlamp restoration kits are sold by many
different suppliers but they break down into
three significant types.
• “Wax and Buff” Kit—This type of kit basically fills in the micro cracks of the polycar-
© 2013—TMC/ATA
bonate lens and it often looks acceptable
for about as long as a nice wax job looks
on a truck or car. The suppliers of this kit
are often well known suppliers of car care
or car wax products. A “wax and buff” kit
is not recommended for commercial truck
applications.
• “Prepare/ Clean, Sand and Clarify/Seal”
Process—This is a much more labor intensive process which involves cleaning
the headlamp often using a product supplied in the kit which may even remove the
yellowing of the polycarbonate material.
This is followed next by using a sanding
tool which removes the coating that was
applied by the headlamp supplier, and
then finally one or two coats of coating
and a sealer are reapplied to finish the
job. This type of kit provides some good
results but may only last between six
months and a year in a commercial truck
application before another treatment would
be required. If significant deterioration has
occurred in the headlamp lens, it may be
time to replace the headlamp to provide
the level of safety that is required for the
individual application.
• “Remove and Restore”—With this solution, the headlamp is removed, assessed
for condition, and (if it is in generally good
condition) sent out to a third-party service
provider that cleans, polishes and recoats
the headlamp using processes similar to
that used by the original manufacturer.
SUMMARY
The most effective way to extend the life of headlamp coatings is to require the vehicle/component
manufacturer to apply the best coating available to
your vehicles’ headlamps. The coatings that just
meet automotive requirements will prove ineffective
in the commercial truck applications.
When it comes to restoration, remember that the more
sophisticated kits frequently require the addition of
another coating and/or sealing compound to perform
as well as the original manufacturer’s coatings.
NOTE: Headlamp restoration kits, in general, will
not restore the headlamp assemblies to their original
condition nor will they last as long as the original
coating.
Proposed RP 172 (T) Ballot Version—
Recommended Practice
VMRS 017
Proposed RP 220D(T)
TIRE TREAD DESIGN SELECTION
PREFACE
The following Recommended Practice is subject to
the Disclaimer at the front of TMC’s Recommended
Engineering Practices Manual. Users are urged to
read the Disclaimer before considering adoption of
any portion of this Recommended Practice.
PURPOSE AND SCOPE
Selecting the proper tread design for an intended
application is important to maximize tire service life
and minimize tire cost per mile. Because selecting
proper tread design is not an exact science, there
is no way to determine suitability for a specific application without actually testing the tire. However,
there are some general guidelines that can be used
to select tread “types” that will fit equipment users’
needs. These guidelines apply to tread design selection for heavy-truck tires.
TIRE TREAD DESIGN
A tread design is usually a compromise of characteristics that enables the tire to provide good service
under a variety of conditions. Truck tire tread patterns
are usually designed to address a variety of needs
in general applications.
Sometimes one performance requirement may have
to be sacrificed in order to obtain others of greater
priority. For example, some over-the-road tires with
deep treads are designed for high mileage, resistance
to penetration and good wet traction. However, if a
fleet needs to maximize fuel economy, a tire design
with shallower tread depth and less aggressive tread
design might have to be selected that may reduce
traction and overall mileage.
Therefore, it is important to prioritize tire needs based
on a vehicle’s application requirements. A list of
typical tire requirements is as follows:
• Good Dirt and Mud Traction
• Good Dry Traction
• Good Snow Traction
• Good Steering Response
• Good Wet Traction
• High Fuel Economy
© 2013—TMC/ATA
•
•
•
•
•
•
•
•
•
•
Long, High-Speed Run Application
Long/Intermediate On-Off Road Application
Short, Intermediate On-Off Road Application
Long Tread Wear
Reduced Noise Generation
Resistance to Cutting/Chipping
Resistance to Irregular Wear
Resistance to Penetration
Resistance to Rib Tears and Curbing
Resistance to Stone Retention
Typical truck tire tread designs used today are
engineered with emphasis on particular service applications. They are classified as linehaul (longhaul),
regional (shorthaul), urban (pickup and delivery),
or vocational (on/off road). Tires are also designed
with special performance characteristics, such as
providing high fuel economy and delivering good
performance in high torque drive applications.
• Linehaul—Linehaul trucks normally make
runs that exceed 500 miles and are used by
truckload and less-than-truckload (LTL) carriers. These vehicles run 80,000-200,000 miles
a year and operate on highways.
• Regional—Regional carriers operate within a
limited multi-state area such as the Midwest,
Northeast, etc., and have runs about 250 miles.
Fleets that operate regionally include local
food, manufacturer and petroleum distributors.
They run between 30,000 and 80,000 miles a
year.
• Urban—Urban pickup and delivery fleets
operate just in their local area and run very
short mileages with a high percentage of stops.
Examples of these types of fleets include retail/wholesale delivery, beverage fleets, and
bus operations. Vehicle annual mileage is
usually between 20,000 and 60,000 miles.
• Vocational—Vocational trucks in on-off road
service run both on highways as well as go off
paved roads. These applications on construction, utility and refuse vehicles, for example,
operate in highly aggressive conditions at
limited speeds and run between 10,000 to
70,000 miles a year.
Proposed RP 220D(T) Ballot Version — Issued 1/1988
Revised x/xxxx
Tread patterns designed for linehaul and regional
operations are compounded and designed to produce high tread mileage and low rolling resistance
for improved fuel economy. They are produced
with long-wearing compounds and designs that are
resistant to irregular wear. Deep tread patterns are
provided on drive tires to get maximum mileage and
shallow tread depths are designed for trailer tires to
minimize irregular wear.
Pickup and delivery tread patterns are specially designed to address hazards that urban tires encounter
daily. These treads are specifically compounded
for high turning, low mileage applications that are
resistant to punctures and other road hazards. They
are also designed to provide good wet traction and
resist oil contamination frequently encountered in
urban use.
Vocational treads feature cut-chip resistant compounds and have thicker undertread to resist stone
drilling and protect the belt package.
Table 1 lists the general performance features for
tires in different vocations. Tires designed for one
purpose will generally not perform as well in other
applications. For example, a line haul drive tire will
usually not have the chipping and chunking resistance
that an on/off road tire will have. An on/off road drive
tire will normally not provide the tread wear of a line
haul tire in over-the-road service.
In addition to applications, most tire manufacturers
indicate the targeted wheel position for each tire in
their line. Tires are divided into steer, drive, trailer,
and all position categories.
Once you know which characteristics are most important, you can then select the type of tread design
that best suites the fleet’s needs. There are basically
two types of tread designs: Rib or closed designs
and Lug or traction designs.
RIB DESIGNS
Rib designs have grooves that run circumferentially
around the tire. They can be zigzagged or fairly
straight (see Figures 1 and 2). They are usually used
on steer and trailer positions. Zigzagged grooves
offer more biting edges for traction on wet city streets
and, since they reduce the effects of side forces, they
are ideal for turning and maneuvering in pickup and
delivery operations. Continuous straight grooves roll
in a straight line with little rolling resistance which
is what is usually required for high mileage, high
© 2013—TMC/ATA
Figure 1:
Zigzagged Ribs
Figure 2:
Continuous Straight
Grooves
speed, fuel efficient, linehaul operations. “Defense”
or “Decoupling grooves” which are thin straight
grooves on the shoulders of the tire, act as barriers
to reduce shoulder wear on rib tires. These grooves
are excellent in over the road operations but do not
perform well in urban use since they are prone to
stone retention and tearing as a result of curbing.
LUG DESIGNS
Lug designs have blocks and grooves that cut
across the tread pattern, which add traction and aggressiveness to the tire. They can also have some
circumferential grooves as well. These designs are
usually used on drive axles.
Wide shoulder ribs that are resistant to side forces
permit the use of deep treads that provide long tread
life in line haul operations. These tread designs are
also known as closed shoulder patterns. (See Figure 3.) Open shoulder designs that have blocks on
the shoulder as well as throughout the pattern have
more aggressive traction qualities for operation in
rain, mud and snow. (See Figure 4.)
Lug tires with shallower tread depths resist squirm that
constant turning in short haul operations creates and
are less prone to irregular wear patterns. Drivers may
notice a difference in feel when going from a worn out
drive tire to a new full-depth tire. Tire manufacturers
today produce tires specifically designed for tandem
axle drive and single axle drive tractors.
Figure 3:
Closed Shoulder
Proposed RP 220D(T) Ballot Version — Figure 4:
Open Shoulder
© 2013—TMC/ATA
Proposed RP 220D(T) Ballot Version — UNIDRIECTIONAL DESIGNS
Unidirectional tread patterns are designed to rotate
in only one direction. They are the best choice for
reducing irregular wear in
high mileage operations,
however, some special
efforts must be made to
ensure they are installed
correctly on vehicles.
NOTE: If unidirectional
tires are installed backwards, only a loss of
mileage will result. No
damage will be inflicted
on the casing.
SIPES
Tiny notches along the
edges of grooves and
within the tread blocks
and ribs are called sipes.
Sipes help relieve rolling
stresses that initiate and
spread river/erosion wear.
They are essential in tread
patterns of over the road
tires.
© 2013—TMC/ATA
Figure 5:
Unidirectional Rib
Figure 6:
Sipes
PLATFORMS AND STONE EJECTORS
“Platforms”, “stone rejectors” or “stone ejectors”
are specially designed groove side angles that can
reduce stone retention. This attribute is important in
operations that run over gravel or poor asphalt roads
where casing damage and irregular wear caused by
stone retention is a problem.
CONCLUSION
There are a wide variety of tread patterns available.
Many provide maximum performance in certain
applications but provide diminished performance
in others. The challenge is to select the tread pattern that is best suited to the combination of service
requirements in your particular operation. Here are
some tips:
1. List your operational requirements.
2. Rearrange your requirements in order of importance.
3. Compare your operational requirements
against typical tire operating characteristics.
4. Select the category that most nearly matches
your requirements
5. Select a tire tread pattern from this
grouping.
6. Verify your selection with your tire experts.
7. Validate the performance of the selected tread
design by running a tire test.
Proposed RP 220D(T) Ballot Version — Recommended Practice
VMRS 017, 018
Proposed RP 223D(T)
TIRE SELECTION PROCESS
PREFACE
The following Recommended Practice is subject to
the Disclaimer at the front of TMC’s Recommended
Engineering Practices Manual. Users are urged to
read the Disclaimer before considering adoption of
any portion of this Recommended Practice.
PURPOSE
This Recommended Practice (RP) is intended to make
the tire purchaser, fleet operator, or maintenance
manager aware of major items for consideration, and
to provide a step-by-step thought process for selecting
the best type of tire for the application. The following
sections provide a brief explanation of the various tire
selection criteria that must be addressed. A summary
of considerations is also listed to enable the decision
maker to identify advantages and disadvantages of
each of the selection criterion.
While the considerations may not be all-encompassing, they point out the major issues that should be
dealt with before selecting a tire. Because of the
pace of technology change in the tire industry, certain
considerations may become less important while new
ones may arise from time to time.
TIRE SELECTION AND FLEET
OPERATION CONSIDERATIONS
When spec’ing tires, it is important to know what
type of vocation the vehicle is going to operate (e.g.,
linehaul, regional, urban pickup and delivery, on-off
road, etc.). Linehaul trucks normally make runs that
exceed 500 miles, regional carriers operate within a
limited multi-state area such as the Midwest, Northeast, etc., and have runs of about 250 miles, and
pick-up and delivery fleets operate just in their local
area. Vocational trucks in on-off road service run
both on-highway and on unpaved roads.
Tires designed for on-highway operations are
compounded and designed to produce high tread
mileage and low rolling resistance for improved fuel
economy. They are also produced with long-wearing compounds and tread patterns that are resistant
to irregular wear. Deep tread patterns are provided
on drive tires to get maximum mileage and shallow
© 2013—TMC/ATA
tread depths are designed for trailer tires to minimize
irregular wear.
Urban tires are specially designed to address the
hazards that pickup and delivery tires encounter daily.
Their treads are specifically compounded for highturning, low-mileage applications that are resistant
to punctures and other road hazards. They are also
designed to provide good wet traction and resist oil
contamination frequently encountered in urban use.
Their sidewalls are designed to minimize damage
from curbing and have special protector ribs to absorb
shock and protect the sidewalls from damage.
It is important to select the right tire for a given application. Spec’ing or substituting tires in the wrong
application will defeat their purposes. On-highway
tires used in urban operations would tend to fail prematurely due to sidewall abrasion and road hazards.
Their advantages of high mileage and fuel efficiency
would not be attained. On the other hand, urban
tires will not perform well in longhaul, on-highway
operations either. They will wear out quickly, run hot,
and consume fuel. Their advantages of scuff and
penetration resistance would not be utilized.
That being said, there are tires that are designed
to work in multiple service applications for fleets
that operate vehicles in different vocations, such as
regional and local. While these tires will not perform
as well as tires specifically designed for a particular
service vocation, they are a good compromise for
multi-duty vehicles.
VEHICLE CONSIDERATIONS
A. Tire Space Restrictions
New Vehicles—A prospective owner can be creative
in spec’ing a new vehicle to meet specific needs.
Tires and wheels, however, may limit this creativity
since they must be capable of carrying the expected
load and be made to certain minimum dimensions.
The fleet owner can choose from several types of
tires that can carry the anticipated load, but may be
forced to redesign a vehicle’s overall dimensions if the
tires that can carry the load are larger than originally
Proposed RP 223D(T) Ballot Version — Issued 1/1988
Revised x/xxxx
desired. The first thing to consider when purchasing
a vehicle is the vehicle's factory recommendations
In-Service Vehicles—After a vehicle has been operating in a fleet, tires similar to the original equipment
fitments are usually a good choice when replacing the
first set of tires. These tires will usually provide the
best service in the application for which the vehicles
were originally designed.
The original set of tires on the vehicle should be
inspected at regular maintenance intervals and
especially before replacing them with another set
of tires. Any irregularities observed could be signs
of mechanical, alignment, and/or fitment problems.
Compare any unusual wear conditions to those shown
in TMC RP 219C, Radial Tire Conditions Analysis
Guide. This will help to identify any problems found
and provide the recommended corrective action
needed. Each fleet service application can present
a different set of conditions for vehicles. Condition
variables such as loads, speeds, routes, weather,
terrain, and distances traveled can all cause differences in how the tires and wheels perform.
If a vehicle is being used in a different application
or service than it was originally designed, a different
combination of wheels and/or tires may be required
to make the vehicle perform as desired. Failure to
install the correct, application specific tire/wheel
setup for a changed service operation could result
in poor handling, irregular wear, and possibly even
tire/wheel failures in severe applications.
Space restrictions are more inflexible when changing
the type or size of tires used on existing equipment.
Not only must a tire be selected that can carry the
load, it must fit in an existing space. In addition,
when changing tire sizes on an existing power unit,
consideration must be given to the effects the new
size tire will have on the vehicle gear ratio, road
speed and electronics.
Tire Clearances—In order to select a new tire size
for a given application, the dimensional clearance
of the tire must be acceptable. The following define
those areas that must be checked:
1. Vertical Clearance is the distance between
the top of the tire tread and the vehicle immediately above it. This clearance varies as
the axles operate. The vertical movements of
the whole axle in relation to the chassis are
normally limited by an axle stop. To determine
vertical clearance, subtract 1.5 times the axle
© 2013—TMC/ATA
stop clearance from the total clearance above
the tire at rest.
2. Front Tire Clearances are the distances between the front tires (on both steering lock
positions) and the vehicle. Clearances of front
wheels must be checked by turning the wheels
from full left lock to full right lock, and at the
same time observing full jounce and rebound
at each end of the axle. At the extremes of left
and right and full jounce, the tires should clear
all parts of the vehicle by 1.5 inches in static
condition.
3. Overall Width—When fitting larger or wider
tires to an existing vehicle, the overall width
across the dual tires is increased by half of the
increase in the section width of each outside
tire and the increase in offset of each outside
wheel. The overall width across the tires is
measured at the twelve o'clock position and not
at the lower side (six o'clock position) where
the tires deflect due to load. When using tire
chains, a minimum of two inches more clearance is needed to provide clearance between
the dual assembly.
B. Rims and Wheels
The selection of rims or disc wheels goes handin-hand with the selection of tires. When ordering
new equipment, specifying the wheel system type
and recommended rim for the tire size selected will
ensure proper fit, form and function.
The tire or rim/wheel manufacturer’s data book or
Tire & Rim Association Yearbook shows approved
wheels/rims for each tire size.
When selecting the wheel or rim type, it is important
to determine the operating conditions to which the
wheel or rim will be subjected. Conditions to consider
are loads, speeds, road surfaces, tire pressure, tire
size, and wheel material such as steel and aluminum.
Caution is necessary in selecting wheel offsets to ensure proper tire spacing, body and chassis clearance,
and overall track width. If dual tires are used, dual
spacing and tire clearance must be considered.
In addition, the wheel must also have load and inflation ratings sufficient for the tire in the intended
application. When replacing wheels on a vehicle and
the wheels have performed satisfactorily, replace
them with the same size and offset.
When purchasing replacement wheels, decide
whether steel or aluminum is best suited to the fleet’s
Proposed RP 223D(T) Ballot Version — (at 90 degrees to the centerline of the tire), and are
typically made with one steel body ply or multiple
body plies of other materials.
Under the tread area, the radial tire usually has three
or four plies or belts made of steel cord or other
material to stabilize the crown area and offer better puncture resistance. The radial sidewall area is
generally very flexible and the tread area is normally
much stiffer. See Figure 1.
Bias Ply Tire Considerations
• lower initial tire purchase price.
Figure 1
application. When purchasing multi-piece rims, ensure that all components match. For more detail in
selecting the correct wheel/rim, refer to TMC RP 211C,
Rim and Wheel Selection and Maintenance.
C. Radial and Bias Tire Construction
There are two basic types of tire construction—radial
and bias. Radial tires are the most durable and costeffective construction and make up over 95 percent
of the original equipment and replacement market.
Bias ply tires are constructed of overlapping crossed
layers of cord material and are typically made with
nylon, polyester, or other materials. The crossed
plies run on a diagonal from tire bead to tire bead
and comprise a generally stiff sidewall area.
Radial ply tires are made with the cord material
running in a radial or direct line from bead to bead
Tube-Type
Radial Tire Considerations
• improved treadwear performance.
• improved retreadability.
• higher fuel efficiency.
• lower susceptibility to tread punctures.
• better traction characteristics.
• reduced heat build up.
D. Tubeless and Tube-type Tires
The tubeless tire is similar in construction to a tubetype tire, except that a thin layer of air and moistureresistant rubber is used on the inside of the tubeless
tire from bead to bead to obtain an internal seal of
the casing. This eliminates the need for a tube and
flap. See Figure 2.
The two types of tires require different rim configurations: the tubeless tire uses a single-piece wheel;
and the tube-type tire requires a multi-piece wheel
assembly. Both tires, in equivalent sizes, can carry
Tubeless
Tube
Flap
One-Piece
Rim
Multipiece
Rim
Rim Diameter Difference — 2-1/2 inches
TUBE-TYPE TIRE
TUBELESS TIRE
Figure 2: Tire Construction
© 2013—TMC/ATA
Proposed RP 223D(T) Ballot Version — the same load at the same inflation pressure. However, tubeless tires generally offer more benefits than
tube-type tires in linehaul operations.
Tubeless Tire Characteristics vs. Tube-type:
• improved mounting safety due to use of a
single-piece wheel.
• reduced weight/lighter tire-wheel assembly.
• reduced maintenance and parts inventory.
• improved bead durability from less brake drum
heat resulting from higher wheel clearance.
• improved crown and sidewall durability potential from cooler running tubeless casing.
• better lateral stability from lower section
height
• reduced downtime from punctures.
E. Tire Type
Standard Aspect Tires (90 Series)
The standard (90 series) tubeless tire is taller, narrower, and generally heavier than a low-profile tire.
Because of its tall sidewall height, it deflects more
than a low profile as it rolls, causing more heat and
rolling resistance and is less fuel-efficient. Due to its
greater deflection, a standard tubeless tire generally
will ride smoother than a low-profile tire, dampen
more road irregularities, and be more durable and
resistant to impact damages. Standard aspect tires
are commonly used in pickup and delivery and on/off
road type applications.
TABLE 1: CONVENTIONAL VS. LOWPROFILE TIRE COMPARISON
(Example of Typical Dimensions)
11R22.5
Diameter
Section Width
Tread Depth
Rim
*Static Loaded
Radius (SLR)
RPM
295/75R22.5
(Low Profile)
41.3"
10.8"
19/32"
8.25"
40.2"
11.2"
19/32"
8.25"
19.3"
503
18.8"
517
Load Inflation (kg/kPa; lbs/psi)
Single kg.
lbs.
Dual kg.
lbs.
2800/720
6175/105
2650/720
5840/105
2800/760
6175/110
2575/760
5675/110
*Static Loaded Radius is the difference from the road surface
to the rim horizontal centerline at rated load and pressure.
© 2013—TMC/ATA
Low-Profile (Low-Aspect Ratio) Tires
The low-profile tire is not as tall as the standard tire
so vehicle floor height will be lowered. The tread is
generally wider and the sidewall height shorter. This
results in less sidewall deflection and less heat as
it rolls, so less rolling resistance is generated and
better fuel economy results. The shorter sidewalls
also provide a stiffer ride and less impact damage
resistance. The low-profile tire is also lighter than
the equivalent standard tire and is more commonly
used in linehaul and regional haul, high-speed operations. Both the standard aspect and low-profile
tires of equivalent wheel diameters will carry virtually
the same loads.
The advantages of low-profile tires include:
• potential for improved treadwear (less irregular
wear) on steer and trail axles.
• lighter weight.
• improved stability and handling from higher
lateral spring rate and lower center of gravity.
• more susceptible to sidewall curb damage.
When changing to low-profile tires, there are drivetrain/gearing considerations that must be made at
both the original equipment and replacement levels.
The engine speed, transmission, drive axle gear ratio
and tire RPM (revolutions per mile) will all be affected.
The objective is to obtain the most fuel efficient engine RPM/ground speed relationship consistent with
service condition requirements.
The effect on road speed at the same engine speed
using a 55 MPH base depends upon which conventional aspect ratio and low profile tires are involved.
Generally, if the change in the tire RPM is three percent
or less, a gearing change is not required. However,
the engine electronic control module (ECM) RPM
parameter must be recalibrated to ensure accurate
speedometer readings.
Wide-base Tires
A wide-base tire is approximately one and a half times
wider than the same diameter size standard dual tire
and has a higher load carrying capacity. Standard
wide-base sizes are 385/65R22.5, 425/65R22.5, and
445/65R22.5. Currently, the tire’s primary application
in North America is on vehicles whose front axle
loads exceed the capacity of standard tires. Tankers, refuse haulers and construction vehicles such
as cement mixers are prime examples. In addition to
increased load capacity, these larger tires improve
flotation versus conventional size tires.
Proposed RP 223D(T) Ballot Version — Common aspect ratio categories of medium truck tires are as follows:
- 100
Tube-type conventional sizes (10.00R20)
Section Height = Aspect Ratio
- 90
Drop center tubeless (11R22.5)
Section Width
- 60-70-75-80 Low profile (295/75R22.5, 255/70R22.5)
- 65-55-50-45 Wide-base singles (445/50R22.5, 445/65R22.5)
NEW TIRE DIMENSIONS
Overall
Diameter
Section
Height
Rim Width
Section Width
OverallDiameter
Width
Overall
Nominal
Rim
Diameter
“Aspect Ratio” is defined as the percent of the section height to the section width of the tire.
Fig. 3: Aspect Ratio
TIRE SECTION
WIDTH
WHEEL
OFFSET
TIRE CLEARANCE
DUAL (OR CENTERTO-CENTER) SPACING
VEHICLE
CLEARANCE
(V/C)
TIRE SECTION
WIDTH
WHEEL
OFFSET
Fig. 4: Overall Width, Dual Tires
© 2013—TMC/ATA
Proposed RP 223D(T) Ballot Version — Low-profile wide-base tire sizes are:
• 445/50R22.5, which replaces low-profile 22.5
duals, and;
• 455/55R22.5, which replaces 11R22.5 and
low-profile 24.5 duals on the drive and trailing
axles. These tires are used in all vocations
from linehaul to sanitation.
The advantages and disadvantages of wide-base tires
vs. duals in many performance categories depend on
specific vehicle configurations and operations.
Advantages include:
• Lower tire and rim weight/increased payload.
• Ease of maintenance—no inside dual tire pressure to match or maintain.
• Elimination of mismatched dual height and/or
pressure which could provide more uniform
wear.
• Reduced tire and rim inventory.
• Improved fuel economy.
• Potential to lower rig center of gravity for improved handling and stability.
Disadvantages include:
• Tires/wheels not standardized in fleet.
• Eliminated “limp home” capability.
• Possible increased treadwear rate.
• Heavy assembly weight.
Possible legal restrictions of non-steer axle application
of wide-base singles should be thoroughly investigated
before finalizing size selection.
In retrofit applications, care must be taken to properly
select wheel/rim offsets to maintain a tracking width
for acceptable stability.
F. Matching Tires for Speed and Axle Weights
In a tire selection process, consideration must be
given to selecting a tire size and load range which at
least equals the vehicle placard requirements by axle
position (steer, drive, or trailer). All highway truck tires
have load limits established for tires used in normal
highway service. Therefore, both the carrying capacity
and speed implications must be considered.
The load that each tire carries can be determined on
existing vehicles in the fleet by running the loaded vehicle over scales and recording the individual weights
that each axle is supporting. All tire manufacturers
publish load and inflation tables that can be used to
determine the proper inflation pressure at various
© 2013—TMC/ATA
loads. This information can also be found in the Tire
and Rim Association Yearbook. In addition, vehicle
manufacturers usually include a recommended cold
air pressure in their door specification placards.
To determine the proper inflation pressure a vehicle’s tires should have, the following information is
needed:
• Size and load rating of the tires installed on
the vehicle
• Weight carried on each axle.
• Number of tires on each axle
• Maximum speed that the vehicle travels during
its operation
• Operational history
For example, when selecting tires for a tractor-trailer
combination with a gross combination weight (GCW)
of 80,000 lbs. and an axle weight distribution of 12,000
lbs. on the steer, 34,000 lbs. on the tandem drive,
and 34,000 lbs. on the tandem trailer axles, common conventional tire sizes used are 295/75R22.5
(275/80R22.5), 285/75R24.5 (275/80R24.5),
11R22.5R and 11R24.5 Load Range G. The load
and inflation schedule for these sizes is shown in
Table 2.
Tire manufacturers are required to determine the
speed rating of their truck tires. highway tires are
generally rated at 65-75 MPH. Some heavy application on/off highway tires are rated at 55 MPH or
less. These tires are considered “speed restricted”
and must have “55 MPH or lower” molded into their
sidewalls. Consult your tire supplier for speed rating
information.
The Tire and Rim Association has established inflation pressures for load limits at various speeds for
truck tires used on improved surfaces. Consult your
individual tire manufacturer for specific recommendations to meet your operating condition.
G. Tread Design Selection
Selecting the proper tread design for an intended application is very important for obtaining the maximum
potential from tires and thereby lower tire expenses.
Proper tread design selection is not an exact science,
but there are certain general rules and guidelines
which, if followed, can lead to selecting a tread design
that will give the maximum desired performance for
the service application in a particular fleet. For help
in selecting tread designs, see TMC RP 220C, Tire
Tread Design Selection.
Proposed RP 223D(T) Ballot Version — TABLE 2: TIRE LOAD LIMITS (LBS.) AT VARIOUS COLD INFLATION PRESSURES
(Pressure is Minimum for the Load, Maximum Speed of 60 MPH)
Inflation Pressure (psi)
Size
Usage
70
75
80
85
90
95
295/75R22.5
Dual
Single
4095
4500
4300
4725
4540
4940
4690
5155
4885
5370
5070(F)
5510(F)
275/80R22.5
Dual
Single
4300
4725
4540
4940
4690
5155
4885
5370
5070(F)
5510(F)
285/75R24.5
Dual
Single
4340
4770
4540
4940
4740
5210
4930
5450
5205(F)
5675(F)
275/80R24.5
Dual
Single
4340
4770
4540
4940
4740
5210
4930
5450
5205(F)
5675(F)
Inflation Pressure (psi)
Size
Usage
100
105
110
115
120
295/75R22.5
Dual
Single
5260
5780
5440
5980
5675(G)
6175(G)
5795
6370
6005 (H)
6610 (H)
275/80R22.5
Dual
Single
5260
5780
5440
5980
5675(G)
6175(G)
5795
6370
6005 (H)
6610 (H)
285/75R24.5
Dual
Single
5310
5835
5495
6040
5675(G)
6175(G) 5860
6440
6175 (H)
6780 (H)
275/80R24.5
Dual
Single
5310
5835
5495
6040
5675(G)
6175(G) 5860
6440
6175 (H)
6780 (H)
(F) = Load Range F
(G) = Load Range G
(H) = Load Range H
Numbers after letters denote international load index.
FLEET OPERATION CONSIDERATIONS
When evaluating the many tire options available for
any given vehicle application, there are numerous
management considerations in addition to the mechanical considerations already covered. While these
considerations apply most directly when spec’ing new
equipment, they also can be used to reevaluate tire
selection prior to tire replacement. Some examples
of fleet operation considerations include:
• availability of various products and service
maintenance
• tire purchase price vs. performance (cost-permile)
• financial inventory investment and space requirements
• maintenance training for personnel
• retreadability/repairability costs and servicing
• warranty and adjustment servicing
• leading edge or “experimental” product availability
© 2013—TMC/ATA
• effects of non-standardization
• effects of tire down-sizing on vehicle gearing
and braking
• timing for phase-in or changeover programs
• legal or contractual requirements
RETREADING
Retreading your worn tires or purchasing retreads
from a dealer can provide new tire dependability and
performance at a fraction of the cost of a new tire.
When selecting new tires, purchase those that are
designed to be retreaded. Follow prescribed maintenance and avoid regrooving which may damage the
valuable casing. Retreaded tires should:
• provide equivalent dependability, service,
performance
• reduce overall cost per mile
• conserve natural resources
• tread designs available for all applications
Proposed RP 223D(T) Ballot Version — TABLE 3
INTERNATIONAL LOAD INDEX NUMBERS
Load Index: A numerical code associated with the maximum load a tire can carry at the speed indicated
by its speed symbol under specified service conditions.
© 2013—TMC/ATA
Proposed RP 223D(T) Ballot Version — APPENDIX I
EXPLANATION OF TRUCK TIRE DESIGNATIONS
TIRE SIZE DESIGNATION
LOAD IDENTIFICATION
OPTIONAL SERVICE
DESCRIPTION
LOW-PROFILE TIRES
295 / 75 R 22.5
Rim diameter in inches
Load Range
(15° tapered bead)
F
Rim diameter in inches
Load Range
(15° tapered bead)
Radial
Aspect Ratio
Cross Section (mm)
R 22.5
L
Load Index
(Single/Dual)
Speed
Symbol
Cross Section (mm)
STANDARD ASPECT TIRES
11 141/144
Radial
Aspect Ratio
245 / 70 R 19.5
G
119/121K
Load Index
(Single/Dual)
Speed
Symbol
Service Description: A service designation, which
is distinct from the size designation, consisting of
the Load Index (Single/Load/Dual Load, where
applicable) and Speed Symbol
G
Rim diameter in inches
Load Range
(15° tapered bead)
142/144
L
Load Index
(Single/Dual)
Speed
Symbol
Radial
Cross Section (in.)
Speed Symbol: Indicates the speed category at
which the tire can carry a load corresponding to its
Load Index under specified service conditions.
TUBE-TYPE TIRES
10.00 R
20
G
Rim diameter in inches
Load Range
Radial
Cross Section (in.)
NOTE: Load indexes and speed symbols are used in
Europe but are not recognized by the U.S. Department
of Transportation (DOT) on truck tires.
© 2013—TMC/ATA
SPEED SYMBOL
F
G
J
K
L
Proposed RP 223D(T) Ballot Version — 142/144
L
Load Index
(Single/Dual)
Speed
Symbol
SPEED CATEGORY
50 MPH (80 km/h)
55 MPH (90 km/h)
62 MPH (100 km/h)
68 MPH (110 km/h)
75 MPH (120 km/h)
APPENDIX II
TIRE SELECTION PROCESS WORK SHEET
STEP 1
a. Record manufacturer axle weight ratings.
________
Steer
_________
Drive
__________
Drive/Trail
___________
Trail
__________
Trail
b. Axle Weights
________
Steer
_________
Drive
__________
Drive/Trail
___________
Trail
__________
Trail
STEP 2
Check type of service
_______
Long Haul (Linehaul)—Travel on interstate and normal highway roads at maximum speeds
with runs more than 250 miles.
_______
Regional Service—Travel on interstate and normal highway roads at maximum speeds with
runs less than 250 miles.
_______
Urban (Pickup and Delivery)—Most travel between and around city areas.
_______
On-Off-Road—Travel on some highway and secondary roads with possible travel on gravel/
dirt roads.
_______
Off-Road—Travel on mostly secondary and gravel/dirt roads with a potential for tread cutting
due to rocks, debris, etc.
STEP 3
Determine size restrictions
1. If spec’ing for new equipment, provide for adequate tire clearance and brake compatibility.
a. Minimum tire diameter due to brake restrictions
____________________
b. Maximum tire diameter desired
____________________
2. If retrofitting tires on existing equipment, will rim size change?
a. [
] No (State Rim Size)
____________________
b. [
] Yes (Select new rim size in Step 10)
If wheel size becomes larger (change from dual tires to wide-base tires or to larger dual tires), determine
present tire clearances (include chained dimensions, if used):
(1) Vertical Tire Clearance
____________________
(2) Front Wheel Clearance
____________________
(3) Overall Width of Present Tire
____________________
(4) Overall Diameter of Present Tire
____________________
(5) Current Wheel Offset
____________________
(6) Overall Width Across the Tires
____________________
(7) Dual Spacing (if applicable)
____________________
(8) Turning Radius Clearance
____________________
If wheel size decreases, check brake compatibility
© 2013—TMC/ATA
____________________
Proposed RP 223D(T) Ballot Version — 10
STEP 4
Write in type of tires to be used — Duals or Wide-Base
____________________
STEP 5
Write in type of construction to be used—Radial or Bias
____________________
STEP 6
Write in type of air retention construction—Tube-type or Tubeless ____________________
STEP 7
Select tire size from Tire and Rim Association tables or tire manufacturers’ data books using the tire
described in Steps 4 through 6. Do this by cross checking the axle weights and speed restrictions to be
sure the tires can carry the maximum axle load recorded in Step 1 at operational speeds.
Tire Size __________
Dual Load __________
Single Load __________
at __________ psi
If maximum loads cannot be attained with the initial tire desired, a change in either Steps 3(1), 4, or 5
must be made. Repeat Step 7 until a tire size with the necessary carrying capacity is selected.
NOTE: Tire and Rim Associations tables contain general industry standards. In some cases, tire manufacturer data books list higher maximum loads.
STEP 8
Write in selected tire’s dimensions from Tire and Rim Association tables or tire manufacturers’ data.
Overall Diameter
____________________
Overall Width
____________________
Revolutions per Mile
____________________
Minimum Dual Spacing ____________________
1. If spec'ing new equipment, redesign space restrictions if adequate clearance and brake compatibility
are not afforded, or return to Step 8 and select another size tire.
2. If retrofitting tires on existing equipment and larger size tires than presently used are selected, determine clearances:
a. Vertical Clearances:
Vertical Tire Clearance of Present Tire
____________________
Overall Diameter of Present Tire
+
____________________
=
____________________ (Subtotal)
Overall Diameter of Selected Tire
-
____________________
Vertical Tire Clearance
(Ask vehicle/suspension manufacturer
for minimum clearance required.)
=
____________________
Overall Vehicle Height
___________________
© 2013—TMC/ATA
Proposed RP 223D(T) Ballot Version — 11
b. Front Tire Clearance:
Vertical Clearance of Present Tire
____________________
Overall Diameter of Present Tire
+
____________________
=
____________________ (Subtotal)
Overall Diameter of Selected Tire
-
____________________
Vertical Front Tire Clearance
(Must be a positive number.)
=
____________________
c. Overall Width:
Overall Width of all tires across the axle
at present (physical measurement)
Overall Width of one current outside tire
____________________
- ____________________
= ____________________ (Subtotal)
Overall Width of one selected outside tire + ____________________
= ____________________ (Subtotal)
- ____________________
Offset of both current outside wheels
= ____________________ (Subtotal)
Offset of both selected outside wheels
+ ____________________
Overall Width (Must be 102" or less.)
____________________
If all clearances are not suitable, return to Step 7 and select a smaller size tire.
STEP 9
Select wheel/rim from Tire and Rim Association tables or wheel/rim manufacturers’ catalogs. Check to
see that load and inflation pressure ratings are adequate (compare with Single Load and Pressure in
Step 7).
Wheel Size __________
Load Rating __________
at __________ psi
STEP 10
Select tread designs for steer, drive, and trailer positions using TMC RP 220, Tire Tread Design Selection.
STEP 11
Incorporate fleet operation considerations at this point. Compute gear ratio changes if appropriate.
© 2013—TMC/ATA
Proposed RP 223D(T) Ballot Version — 12
Recommended Practice
Proposed RP 312B(T)
VMRS 053-999-002
QUALIFYING QUESTIONS FOR EVALUATING
AFTERMARKET DIESEL FUEL ADDITIVE PACKAGES
PREFACE
The following Recommended Practice is subject to
the Disclaimer at the front of TMC’s Recommended
Engineering Practices Manual. Users are urged to
read the Disclaimer before considering adoption of
any portion of this Recommended Practice.
PURPOSE AND SCOPE
This Recommended Practice (RP) is intended to
provide a list of questions fleet maintenance managers should keep in mind when considering the use of
diesel fuel additives. This will assist in making intelligent choices in the selection of fuel additives.
NOTE: The fact that an additive may qualify as acceptable under the guidelines of this RP does not imply
any guarantee of positive performance. The onus is
upon users to establish performance requirements
and cost/benefit ratios with additive suppliers on an
individual basis.
QUESTIONS FOR EVALUATING FUEL ADDITIVES
1. Will the product measurably affect the cetane
number of fuel? (Reduced cetane may cause
starting difficulties, especially in cold weather,
and can cause knocking and rough engine
operation from ignition delay.)
2. Will product measurably increase the ash content of the fuel? If yes, what is the ash increase
in parts per million in the fuel when the additive
is blended at the maximum recommended
dosage? ASTM D 975 Specs for No. 2 diesel
fuel allow a maximum of 0.01 percent ash by
weight which may approximate to 100 ppm.
High ash levels in the fuel can cause higher
rates of ring and piston groove wear that may
need to be evaluated by fleets using high ash
fuels. High ash can also increase the level
of particulate emissions from diesel engines
and may need to be evaluated to determine
the impact, if any, on emissions requirements
that the equipment user is required to meet.
©2013—TMC/ATA
High-ash fuel may also reduce the number
of miles/hours between service intervals on
certain types of aftertreatment. On other types
of aftertreatment, high-ash fuels might reduce
the life of aftertreatment components. Thus,
before an additive is used, the impact on
aftertreatment devices should be evaluated.
3. Does the product contain any metallic compounds or any other elements other than
hydrogen, carbon, nitrogen, or oxygen? If
yes, specify compound and amount. Also,
is the product EPA registered? All gasoline
and diesel motor vehicle fuel additives are required to be registered in accordance with the
regulations at 40 CFR 79. Lists of registered
gasoline and diesel additives are available at
http://www.epa.gov/otaq/fuels/index.htm.
(Some metallic trace elements can be beneficial as combustion catalysts and/or smoke
suppressors in low concentration of just a few
parts per million when blended in the fuel;
any greater concentration will measurably
increase total ash content as per (2) above.
Some metals can destabilize fuel in storage,
form particularly abrasive ash, or produce
very toxic exhaust emissions; it is recommended that independent specialist advice
be sought before using any additive package
containing metallic compounds. Halogenated
compounds (e.g., containing chlorine, fluorine,
and/or bromine) and sulfur compounds form
highly corrosive acids at the combustion
stage. These acids, when introduced into the
crankcase through downward blow-by, rapidly
deplete the lubricating oil additive package to
form sludge in addition to their corrosive effect
on all metallic engine components.)
4. Will the product measurably increase the vapor pressure and/or reduce the flash point of
the fuel? (If yes, this may cause an explosive
safety hazard and may also be illegal.)
Proposed RP 312B(T) Ballot Version— Issued 5/1981
Revised x/xxxx
5. Will the product significantly change the viscosity of the fuel? (Increased viscosity may lead
to incomplete combustion. Reduced viscosity
may accelerate fuel pump and injector wear
rates from lowering of the inherent lubricity of
the fuel.) See ASTM D975.
6. Will the product complex with sediment or
water, either suspended in the fuel or settled in
fuel tanks, to form sludge suspensions capable
of plugging fuel filters and/or injectors?
7. Will the product remain indefinitely blended in the
fuel, or will it settle out during fuel storage?
8. Does the product contain gasoline or other
solvent hydrocarbons that may cause detrimental side effects on equipment and may be
potential safety hazards?
9. Will the product change the cold weather
performance characteristics of the fuel (i.e.,
cloud point, LTFT, CFPP, and/or pour point)?
Aftermarket additives in low dose concentrations typically do not measurably reduce the
cloud point of the fuel. Cloud point additives
are typically added at the refinery and not as
aftermarket products. Aftermarket additives
may not affect each of the remaining properties. See TMC RP 356, Cold Flow Operability
of Diesel Fuel.
10. Does the additive have any sensitivity to overtreat? If so, what are the consequences?
11. Does the additive clearly state that it meets
all federal and state regulations for ultra lowsulfur diesel (ULSD)? Sulfur content of ULSD
is limited to less than 15 ppm by law for use
in diesel motor vehicles. Improper use of an
additive with greater than 15 ppm sulfur content
may result in a non-complying diesel fuel.
12. Does the product contain a lubricity additive
and if so, is it compatible with the engine oil
and will the additive measurably improve the
HFRR lubricity performance of the fuel? See
ASTM D 6079, High Frequency Reciprocating
Rig (HFRR) Test. (See Table 1.)
13. Does the additive contain antioxidants and a
stability additive? These will help stabilize the
fuel, prevent fuel degradation and prevent peroxide build up in ULSD and Biodiesel. ULSD
is relatively stable, but peroxide formation may
occur and cause embrittlement of elastomers
and rubber seals. Additives that contain antioxidants can prevent peroxide buildup. Refer
to ASTM D975 and ASTM D7467.
14. Does the product contain sufficient corrosion inhibitor? As fuels are more severely
©2013—TMC/ATA
TABLE 1:
HFRR WORLDWIDE SPECIFICATIONS
US < 520 µm at 60º C by HFRR specification
EU (EN-590 Diesel) < 460 µm 60 º by HFRR
Canada < 460 µm at 60 º C by HFRR
• 2800 g by SLBOCLE
• Acceptable Pump Rig Test Rating
- ≥4.0 OPR (Distributor-type fuel injection pump)
- ≤ 5.3 OPR (Rotary-type fuel injection pump)
• Acceptable pump rating in Vehicle Field Test
hydrotreated, they tend to become more corrosive. Fuels have less corrosion protection
as they move downstream through pipelines.
The use of a corrosion inhibitor should be
considered if issues have been identified.
15. Is the additive compatible with biodiesel blends
of fuel? For what percentage of biodiesel (B2,
B5, or greater) is the product rated?
16. Does the additive affect the verification of any
device, retrofit or original equipment, by any
governmental regulatory body?
17. Does the additive affect warranty? Does the
amount of water @ 200 ppm affect warranty?
Check with engine manufacturer for water
contamination allowances.
18. What is the treat ratio? Does the label clearly
state the correct amount of treatment needed
per gallon?
19. Does the additive emulsify or demulsify? It may
suppress water to the bottom, to the fuel/water
separator or through the fuel filter.
OTHER RELATED QUESTIONS
A. Biodiesel
Bio-based fuels tend to be unstable due to increased
amounts of unsaturated components. Over time,
particulates can form in an unstable biofuel which
can lead to more frequent filter changes. Use of a
stability additive can help prevent or minimize the
oxidative deterioration of the biofuel.
1. Are storage tanks containing biodiesel being inspected for particulate contamination?
Biodiesel is a good solvent and can loosen
particulates or sediment in a storage tank.
Proposed RP 312B(T) Ballot Version— These particulates can become dispersed
in the fuel causing increased incidence of
filter plugging. Stability additives containing
dispersants and metal deactivators can help
minimize the solvency effect of the biofuel.
See TMC RP 345A, Diesel Fuel Housekeeping Guidelines, and TMC RP 357, Biodiesel
Blended Fuels.
2. Are storage tanks containing biodiesel being
inspected for water contamination? Biodiesel
is hygroscopic and water contamination can
be an issue. Biodiesel is a good food source
for microbes and with water contamination can
increase microbial activity causing clogged fuel
lines/filters. The presence of water can also
lead to increased incidence of corrosion in
the fuel system as well as handling problems
during cold weather.
GLOSSARY OF TERMS
Cetane Number—A number rating of the ignition
quality of a fuel and the speed at which it will burn.
Biodiesel itself can also be considered an
additive (often put into diesel fuel at low percentages for lubricity purposes). Any biodiesel
blended into diesel fuel should meet D6751
specifications and preferably be produced by
BQ9000 producers. See TMC RP 345A and
TMC RP 357.
Low Temperature Flow Test (LTFT)—A dynamic
test used to evaluate the ability of the fuel to flow
through a filter. This temperature is typically lower
than the cloud point but higher than the pour point
of the fuel.
B. Water Contamination
Some fuel additives claim temporary benefit when
fuel is contaminated with water. They are not intended
to replace good fuel handling practices. Good fuel
handling practices include bulk tank filtration, regularly
removing the water from the bottom of the storage
tank and regular tank cleaning.
Where water contamination is a concern, equip the
fuel system with a fuel/water separator and service
it regularly. Supplemental fuel additives designed
to disperse, emulsify or carry the water through the
fuel system should not be used, as they can disable
or significantly reduce the efficiency of fuel/water
separators, resulting in fuel system corrosion. OEM’s
may allow up to 200 ppm of water to pass through
the fuel system.
Since many fuel additives act as surfactants, their effect on the efficiency of a fuel water separator should
be evaluated by ASTM D7261 test method, which
is a quick measurement of roughly how much water
passes through a coalescing filter in a single pass.
©2013—TMC/ATA
Cloud Point—The temperature at which paraffin
wax crystals begin to form and separate out of fuel.
(This may lead to plugged fuel filters in cold weather
operations for vehicles without fuel heaters.
Cold Filter Plugging Point (CFPP)—A dynamic
test used to evaluate the ability of the fuel to flow
through a filter. This temperature is typically lower
than the cloud point but higher than the pour point
of the fuel.
Flash Point—The temperature at which enough
volatile material evaporates so that a combustible
mixture of fuel and air is formed above the fuel.
Pour Point—The lowest temperature at which fuel
will flow or pour. (Fuels which are not properly treated,
either by blending with a lighter distillate or by the
use of a wax crystal modifier/pour point depressant
additive, may gel in saddle tanks and fuel lines if
ambient temperature goes below the pour point.)
REFERENCES
• ASTM D975, Standard Specification for Diesel
Fuel Oils.
• ASTM D6079, Standard Test Method for
Evaluating Lubricity of Diesel Fuels by the
High-Frequency Reciprocating Rig (HFRR).
• ASTM D6751, Standard Specification for
Biodiesel Fuel Blend Stock (B100) for Middle
Distillate Fuels.
• ASTM D97261, Standard Test Method for
Determining Water Separation Characteristics
of Diesel Fuels by Portable Separometer.
• ASTM D7467, Standard Specification for
Diesel Fuel Oil, Biodiesel Blend (B6 to B20).
• TMC RP 345A, Diesel Fuel Housekeeping
Guidelines.
• TMC RP 356, Cold Flow Operability of Diesel
Fuel.
• TMC RP 357, Biodiesel Blended Fuels.
Proposed RP 312B(T) Ballot Version— Recommended Practice
Proposed RP 443 (T)
VMRS 001
IN-CAB CLEANING AND DEODORIZING GUIDELINES
PREFACE
The following Recommended Practice is subject to
the Disclaimer at the front of TMC’s Recommended
Maintenance Practices Manual. Users are urged to
read the Disclaimer before considering adoption of
any portion of this Recommended Practice.
PURPOSE AND SCOPE
The purpose of this Recommended Practice (RP) is
to offer guidelines for the in-cab cleaning and deodorizing of commercial vehicles. It is meant to provide
information on the benefits of establishing a proper
vehicle interior cleaning program. It is not intended
to endorse any single method or chemistry. This
document applies to all commercial vehicles.
NOTE: The information presented was current at time
of publication. Technical improvements in cleaning
technologies, equipment and chemistry may require
re-evaluation at time of protocol adoption.
BENEFITS OF IN-CAB CLEANING/DEODORIZING
In-cab cleaning and deodorizing is incorrectly viewed
by some as an expense with little or no return. This is
not the case. Clean vehicle cabs help lower maintenance costs and reduce potential health risks, which
can increase vehicle safety. Regular cleaning can also
increase the longevity of leather and textiles. Since
a company’s internal and external image is partially
determined by the condition of its fleet’s cabs, a
conscientious cleaning and deodorizing program can
also help project a positive corporate image.
Adhering to a continuous program of interior cleaning
will result in a cleaner and safer operator compartment. For example:
• Clean windows will allow for unobstructed
view of traffic and landscape.
• A clean driver compartment workspace helps
prevents mishaps resulting from clutter.
• Clean vehicle cabs support driver attraction and
retention and increase employee morale.
• Following a regular cleaning schedule helps
reduce the incidence of unscheduled vehicle
downtime.
© 2013—TMC/ATA
• Regular in-cab cleaning and inspection helps
control or prevent infestations of bedbugs,
which are a growing problem.
REGULATORY CONSIDERATIONS
Solid Waste Disposal Options
Personnel should dispose of solid wastes, such as
foodstuffs, various liquids, trash, etc., in appropriate
and approved trash collection bins. Use of a trash
hauling company to a local approved disposal site
or landfill is recommended.
Liquid Waste Disposal Options
Effluent waters generated from cleaning operations are considered to be an industrial wastewater
discharge. The disposal of this effluent needs to be
made in accordance with local, state and federal
discharge water guidelines.
Discharge of waters used in cleaning operations
often may be directed to the local publicly owned
treatment works (POTW) by way of sanitary sewer.
All requirements, conditions and limits must be
observed and required permits must be obtained
Evaporation or incineration may be options worth
reviewing if discharge to the POTW sanitary sewer
is not available.
BUSINESS CONSIDERATIONS
Fleet managers should consider the following when
establishing a vehicle in cab cleaning program:
• Vehicle condition
• Desired cleaning result
• Fleet size
• Fleet type
• Budget
• Frequency
• Designated space availability
• Time constraints/time per vehicle
• Downtime
• Utility requirements/availability
• Capital expenditures
• Throughput
• Available labor
Proposed RP 443 (T) Ballot Version—
Issued x/xxxx
•
•
•
•
Contract work
OSHA compliance issues
Environmental compliance
Administration/control
EMPLOYEE PROTECTION REQUIREMENTS
The use of personal protective equipment (PPE)
should be required during the cleaning process. The
use of gloves, safety goggles and respirator should
be employed by cleaning technicians during the
performance of their cleaning tasks as directed.
IMPORTANT CONSIDERATIONS WHEN USING
THIRD-PARTY COMMERCIAL CLEANERS
Some fleets may choose to outsource the cleaning/
deodorizing function. If so, fleet managers should
consider the following when evaluating third-party
providers of this service:
• What chemicals will the vendor use?
• What is the vendor’s policy on any damage
caused by cleaning chemicals or cleaning
personnel?
• What is the average wait time to complete
cleaning process?
• What is the vendor’s satisfaction guarantee,
if any?
CLEANING SCHEDULE GUIDELINES
Interior cleaning operations should be scheduled
during times when other scheduled or unscheduled
vehicle maintenance or repairs are being made.
The following cleaning schedule serves as a good
guideline for cleaning frequency:
• Daily—Pick up trash and dispose. Wipe up
spills. Clean exterior glass.
• Weekly—Vacuum all seats, carpets and bedding. Change and launder bedding. Clean all
interior glass. Wipe down smooth surfaces
with damp towel.
• Monthly—Hot water extraction spot clean.
• Quarterly—Full and complete hot water extraction cleaning of textile surfaces. Wipe down
all hard interior surfaces. Apply protectant to
all applicable surfaces.
• Semi-Annually—zone and/or sanitize and
deodorize interior of cab.
INTERIOR CLEANING METHODS
:Take care when cleaning around delicate electronics (including gauges) to prevent physical
damage or harm due to excessive moisture. This can
be done by covering delicate electronics with plastic
or restricting cleaning of these components.
© 2013—TMC/ATA
Remove solid debris by hand, broom and/or vacuum
as required. On soft surfaces, (e.g., upholstery, fabric
and carpeting), apply a pre-spray conditioner and
follow up with hot water extraction to loosen, remove
and flush contaminants from soft surfaces.
For restorative cleaning of interior spaces, removal
of seats, consoles and bedding may be desirable or
required. Carpeting may need removal due to damage or debris underneath. Removal of all items to be
laundered will allow personnel to focus on cleaning
the rest of the truck.
Wipe down all solid surfaces with a suitable cleaner
diluted with water to the proper concentration. When
required, brush solution on the surface in a circular
motion to remove soils not removed during the wiping
process. Re-apply as needed.
Wipe all surfaces with a water-dampened towel to remove remaining cleaning agents. Use air movement,
heat and/or dehumidification as required to dry all
surfaces. Clean glass with a glass cleaner or water.
Apply protectants to hard and soft surfaces to prevent
future soiling and prolong cleaning intervals.
Textile Cleaning Methods
There are two general methods available for cleaning fabrics and textiles: encapsulation and hot water
extraction.
a. Encapsulation—Encapsulation cleaner is
scrubbed into surfaces to be cleaned. Debris
is dry vacuumed after dry. Encapsulation
cleaning replaces shampoo cleaning as a
low-moisture cleaning method.
Pros:
- Quick
- Effective on light soils
- Inexpensive
Cons:
- Interim cleaning method, only suitable for
maintenance cleaning
- Post-vacuuming required
- Ineffective on heavy soils
- Not restorative
- Trained labor required
b. Hot Water Extraction—Emulsifier application-cleaning agent is mixed into the supply
tank of hot water extractor. A pre-spray conditioner-cleaning agent is mixed and applied
separately from hot water extractor. Surfaces
Proposed RP 443 (T) Ballot Version—
to be cleaned have pre-spray conditioner
applied and are extracted with clear water in
supply tank. The application of heat improves
the cleaning process and reduces the time
involved.
Pros:
- Restorative
- Effective on heavy soils
Cons:
- Special equipment required
- Trained labor required
- Time intensive
BEDBUG INFESTATION AND TREATMENT
A thorough cleaning will help reduce the extent of
a bedbug infestation, but will not entirely eliminate
them. Additional treatment and preventive measures
will be required.
Bedbugs (Cimex lectularius) are small, flat, parasitic
insects that feed solely on the blood of people and
animals while they sleep. Bedbugs are reddish-brown
in color, wingless, range from 1-7 mm in size (roughly
the size of Lincoln’s head on a penny), and can live
several months without a blood meal, according to
the Centers for Disease Control (CDC).1
Although the presence of bedbugs has traditionally
been seen as a problem in developing countries, it
has recently been spreading rapidly in parts of the
United States, Canada, the United Kingdom, and
other parts of Europe. Bedbugs have been found in
five-star hotels and resorts and their presence is not
determined by the cleanliness of the living conditions
where they are found, according to the CDC.
Bedbug infestations usually occur around or near the
areas where people sleep, hiding during the day in
such places as the seams of mattresses, crevices,
etc. Bedbugs have been shown to be able to travel
more than 100 feet in a night but tend to live within
eight feet of where people sleep.
CDC officials report that bedbugs should not be
considered as a medical or public health hazard.
Bedbugs are not known to spread disease. However,
bedbugs can be an annoyance because their presence may cause itching and loss of sleep. Sometimes
1. Centers for Disease Control (CDC) website,
accessed June 25, 2013. http://www.cdc.
gov/parasites/bedbugs/faqs.html
© 2013—TMC/ATA
the itching can lead to excessive scratching that can
sometimes increase the chance of a secondary skin
infection.
According to the CDC, one of the easiest ways to
identify a bedbug infestation is by the tell-tale bite
marks on the face, neck, arms, hands, or any other
body parts while sleeping. However, these bite marks
may take as long as 14 days to develop in some
people so it is important to look for other clues when
determining if bedbugs have infested an area. These
signs include:
• the bedbugs’ exoskeletons after molting,
• bedbugs in the fold of mattresses and
sheets,
• rusty–colored blood spots due to their bloodfilled fecal material that they excrete on the
mattress or nearby furniture, and;
• a sweet musty odor.
To eliminate infestations of bedbugs, remove all
components and soft goods that can be laundered.
The remaining items can be treated together. Heating the entire area to 118°F for 20 minutes will kill
bedbugs. However, a 90-minute treatment is required
to kill bedbug eggs. During treatment, heat must rise
quickly to prevent migration and the deepest crack/
crevice treated must be elevated to 118°F. Inspect
after treatment for activity.
Spraying and/or fogging with pesticides can be used
as a preventive measure but are not by itself 100percent effective in treating infestations of bedbugs.
Heat is an effective method of initial treatment;
however, pesticides may be required to prevent
recurrence. Covering mattresses with anti-allergen
covers will reduce the incidence of a possibility of
bedbug infestation within the mattress.
IN-CAB FILTERS
Take special care to maintain in-cab filtration systems needed for outside air, recirculating in-cab
and sleeper compartment filtration. These filters are
also important to help prevent pet hair and other
debris from blocking heater/condenser coils. In-cab
filters should be properly maintained according to
manufacturer recommendations and prescribed
maintenance intervals.
ODOR CONTROL AND ELIMINATION METHODS
Routine daily activities generate debris that can
cause odors. Pets, smoking, food storage are also
items that require attention. The first rule of odor
control is to remove the source. Once this is done,
Proposed RP 443 (T) Ballot Version—
there are choices to be made as to the direction of
the treatment.
Deodorants, such as scents, fragrances, offer a quick
response, but their effectiveness is limited and shortlived. Other solutions may offer better results, such
as counteractants, neutralizers/chemical absorbents
and ozone treatments.
• Product application must contact the odor
source
• Trained labor required
Pros:
• Quick
• Easy
• Inexpensive
D. Ozone
Ozone is an oxidizing gas which is introduced into
the odor environment to oxidize the odor. Ozone
treatment does require certain conditions for effective usage:
• Area must be clean and dry
• Temperature must be less than 80°F. (70°F
is optimum. At 60°F, a visible ozone cloud
forms)
• Air movement in area is needed to disperse
ozone
• Relative humidity should be 40 percent or less
(conditioned air)
Cons:
• Odor source remains active
• Short-term solution, limited effectiveness
• Masks problem
Typically, the ozone generator will run in the area
to be treated for about 15-30 minutes. The cleaning
technician will then check the results of the treatment
and reapply if needed.
B. Counteractants
These are typically liquid compounds that use masking and paring agents to mask and/or bind odor
molecules to eliminate unpleasant odors.
Pros:
• Provides thorough cleaning
• Long-term solution
A. Deodorants
These are scents or fragrances that cover up or
overpower an unwanted odor.
Pros:
•
•
•
Cons:
•
•
Quick
Easy
Provides immediate results
Cons:
•
•
•
•
Specialized equipment required
Ozone is toxic to organic matter
Treatment is time intensive
Trained labor required
Odor source remains active
Initially effective, but ineffective over the longterm
• Masks problem
• Labor required
E. Protectants
Protectants may be available for certain materials
that can help prevent absorption of odors and stains.
These solutions are available for leather, vinyl and
various textiles.
C. Specialty Odor Neutralizers
Specialty odor neutralizers work through combined
actions of chemical bonding, physical adsorption and
counteraction.
INCENTIVES
It may be possible to incentivize drivers to perform
interior cab cleaning on a daily, weekly, monthly,
quarterly, semi-annually and/or annual basis. Truck
check-in and check-out procedures can be developed
to help control vehicle condition on driver changes.
Pros:
• Instant results
• Effective for long term solution
• Odor source inactivated
Cons:
• Relatively more expensive than deodorants
and counteractants
© 2013—TMC/ATA
Surprise spot inspections could provide the motivation
to maintain a clean work environment on a regular
basis. Make these inspections of cab interiors part
of the pre-trip check and inspection process.
Proposed RP 443 (T) Ballot Version—
Recommended Practice
Proposed RP 704C(T)
VMRS 034
HEAVY-DUTY LIGHTING SYSTEMS FOR TRAILERS
PREFACE
The following Recommended Practice is subject to
the Disclaimer at the front of TMC’s Recommended
Engineering Practices Manual. Users are urged to
read the Disclaimer before considering adoption of
any portion of this Recommended Practice.
PURPOSE AND SCOPE
The purpose of this Recommended Practice (RP)
is to help equipment purchasers specify a safe and
effective heavy-duty trailer lighting system that is
low-maintenance, durable, and corrosion-free for a
minimum service life of 12 years. This service life
interval should apply to the integrity of all system
connectors, wiring and support components.
This RP covers general design and installation of
heavy-duty wiring for truck trailers, starting with the
inter-vehicular receptacle and covering all aspects
of the trailer lighting system. It defines the expected
performance requirements for these systems; and
augments, with specific requirements, the standards
depicted in Society of Automotive Engineers (SAE),
Truck Trailer Manufacturer Association (TTMA) and
other TMC recommended practices covering trailer
lighting systems.
This RP supplements the U.S. Department of Transportation Federal Motor Vehicle Safety Standards
(FMVSS) and Federal Motor Carrier Safety Regulations (FMCSR) and other applicable state and local
vehicle regulations. Use of this RP does not in any
way relieve manufacturers or equipment users of the
necessity of complying with applicable federal, state
and/or local regulations.
LIGHTING AND HARNESS
SPECIFICATION DEVELOPMENT
Lighting and harness specifications often differ by fleet
vocation. For example, complex electrical systems
used on tanker trailers certainly differ from container
chassis specifications. The first step in developing an
effective trailer lighting and harness system specification is having the equipment purchaser meet with
the component and trailer manufacturers to discuss
©2013—TMC/ATA
the intended trailer application and environment, as
well as review any documented history involving
component physical damage, fleet crash data, and
auxiliary equipment usage. From this meeting, the
trailer and lighting manufacturers can develop an
effective system-based solution to meet the fleet’s
operational needs.
SPECIFICATIONS
A. Voltage
Heavy-duty trailer lighting systems shall be designed
to connect to tractors with standard- or heavy-duty
12-volt electrical systems. Heavy-duty lighting systems, when operated at a minimum service voltage
of 12.8 volts, measured at the SAE J560 primary
tractor-trailer interface connector, shall not have more
than a 0.7 volt drop per trailer when measured at
the rear trailer lamps. The minimum available power
available at the end of the SAE J560 connector that
connects to the trailer shall be 12.5 volts at 10 amps
on each of the circuits.
B. Circuit Protection
The tractor is expected to provide the basic protection
for electrical circuits (i.e., fuses or circuit breakers).
However proper circuit protection maybe required
for other electrical components on the trailer. It is
the responsibility of either the trailer manufacturer or
the fleet to ensure proper circuit protection for other
devices added to the trailer electrical system. See
TMC RP 156, Electrical Circuit Protection Components for more information.
C. Wiring
Proper wiring specification is critical for providing
sufficient power to the lighting and other electrical
components. Knowing the electrical system load
(amperage) for each electrical circuit is imperative
in determining the proper wire size (gauge).
Start with a careful review of anticipated electrical
loads to ensure sufficient potential will be available
to the trailer. If trailers are designed to be used in
tandems or trains of two or more, this important
Proposed RP 704C(T) Ballot Version—
Issued 3/1980
Revised x/xxxx
factor needs to be considered when calculating the
proper wire size.
The wire shall conform to SAE J1128, or other types
of comparable quality or performance. Wiring shall
be in accordance with SAE J1292, SAE J163, and
TMC RP 110C, Low Tension Cable for Heavy-Duty
Truck-Tractor Wiring Systems. In addition, the wiring
circuits shall be bundled into a protective covering
that terminates with a water-resistant, inter-harness
connector.
Wiring size shall be based on the best estimate of
the current needed to support the proper operation of
the lighting, antilock braking system (ABS) electronic
control unit and other planned electrical devices in
the trailer electrical system. To ensure the safe operation of these devices, there needs to be sufficient
wire gauge for the supply side and the ground side
to feed the electrical components on the trailer. See
Section 6.1 of SAE J2174 to ensure proper gauge
wiring is used.
Protective coverings of wiring and harnesses shall
withstand temperature changes (-40 to +176°F) as
per SAE J1128 and shall be readily adaptable to
sealing upon entrance into the junction box. In all
cases, the protective enclosures shall be made of a
material of equal or greater strength than the material
they are protecting.
D. Color Identification
Wiring diagrams and color codings shall be in accordance with Figure 1, TTMA RP 40-73, and SAE
J560 and J1067.
For the typical trailer, the black coded circuit shall
control the two combined front marker and clearance
lamps, rear three identification cluster, the two lower
rear side marker lamps, and the two lower center
markers for trailers more than 30 feet in length. The
brown coded circuit shall control the two combined
clearance lamps, the two tail lamps, and the license
plate lamp.
The blue circuit has been designated as the primary
power supply circuit for trailer ABS. The blue circuit,
once called the auxiliary circuit, can supply power for
other functions but care must be taken to fully evaluate the current draw of auxiliary devices to ensure
compatibility with ABS units.
E. Wiring Installation
The wiring shall be installed so that any element of
the system is accessible for service or repair from
©2013—TMC/ATA
outside the trailer. Wiring and harness must be
protected from abrasion, road splash, grease, oil,
fuel, rubbing, chafing, and loading activity. Routing
through hat sections or ducts is preferred.
The edges of all metal members through which cables
pass shall be de-burred and rolled or bushed with
suitable grommets. Suitable tubing over cables may
be substituted for grommets, if properly secured.
Clips for retaining cables and harnesses should be
rigidly attached to the body or frame member and
to wiring cables or harnesses about a maximum of
every 16 inches.
For Tank Trailers—The complete wiring system,
including lamps, connectors, molded connectors,
junction boxes, receptacle boxes (with gasketed
cover plates), conduits, and fittings must be provide
resistance to water and spray. Junction boxes must
have provisions for sealing the conduit to the box.
Use Ingress Protection (IP67) rated products/components whenever possible (contact supplier for
more information).
Conduits for Tank Trailers—Wiring must be carried in
tubing or jacketed with appropriate materials. Loom
or other similar fabric tubings are not acceptable. The
conduit shall be adequately supported at intervals
to prevent failure due to vibration and snow, ice, or
mud accumulation.
F. Modular Circuits
Where harnesses are used, the system should be
designed to provide modularity of harness interconnects to specific circuits to facilitate any subsystem
circuit replacement.
The main harness shall have full uninterrupted
continuity (including ultrasonic splices) from the
front receptacle to the rear main connector branch.
Separate sub-harnessed modules are to be used for
the left tail, stop, turn, and clearance lamp circuit;
right tail, stop, turn, and clearance lamp circuit; side
marker and ID lamp circuit; trailer receptacle; and the
combined front marker and clearance circuits. Where
possible, the combined front marker and clearance
lamps should be connected to the front receptacle
(exceptions dump trailers, and other unique applications). See Figure 1.
G. Connections
Electrical connections shall meet corrosion resistance
requirement of SAE J2139 and corrosion prevention
compound shall be used on connectors. Electrical
connections between the wire harness and the lamps
Proposed RP 704C(T) Ballot Version—
NOTE: This trailer is
shown with two (2)
front upper marker/
clearance lamps, if
installed properly a
single PC rated lamp
can be used.
Conductor No.
1
2
3
4
5
6
7
Color
Key
Lamp and Signal Circuits
White
Ground Return To Towing Vehicle
BlackX
Side Marker and Identification Lamps
Yellow
Left-Hand Turn Signal and Hazard Signal
Red
Stop Lamps and Anti-Lock Devices (When Installed)
Green
Right-Hand Turn Signal and Hazard Signal
Brown
Tail, Combined Rear Clearance, and License Plate Lamps
ABS/AUX
Blue
ABS, Auxillary, Optional Lamps, Dome, Etc.
Figure 1: Trailer Lighting Wiring Diagram
©2013—TMC/ATA
Proposed RP 704C(T) Ballot Version—
Figure 2: SAE J2577/TMC 153 Connector Interface
should utilize the new SAE J2577 connector systems
(see Figure 2) as specified in TMC RP 153, Lamp
to Connector Interface Guidelines).
Terminals and connectors shall be weather resistant.
Harness connections shall be accomplished by a
positive mechanical means.
Jumper connector sockets and plugs shall conform
to SAE J560, TTMA RP No. 40, and TMC RP 107C,
Seven Conductor Truck-trailer/Converter Dolly
Jumper Cable And Connector Selection. (See Figures 3 and 4.)
Pigtail connections exceeding 12 inches in length
shall conform to the wire gauge requirements for
Fig. 3: Jumper Connector Receptacle
©2013—TMC/ATA
Proposed RP 704C(T) Ballot Version—
Fig. 4: Jumper Cable Plug
that circuit in the main wiring system of the vehicle.
Pigtail connections between 6-12 inches in length
may not use wire sizes smaller 20 gauge. The wire
used for pigtail connections shall conform to the
requirements of SAE J2174.
H. Grounding
A dedicated ground return system is preferred for all
electrical systems. Chassis grounds may be used to
supplement the independent ground as long as the
connection provides trouble-free performance for a
12-year period.
©2013—TMC/ATA
I. ABS Power
Supply power for ABS units shall be evaluated in
accordance with TMC RP 137 and RP 141.
J. Exterior Lighting
Trailer exterior lighting is a very important aspect of
the combination vehicle safety system. Providing sufficient voltage to the lighting system is an important
means of ensuring that the system will be effective.
The key elements are as follows:
• selecting lighting locations that avoid physical
damage,
• ensuring sufficient voltage to the electrical
Proposed RP 704C(T) Ballot Version—
devices on the trailer,
• using sealed connectors to ensure long life
and resistance to corrosion,
• making sure the location meets the legal and
visibility requirements, and;
• avoiding installation mistakes that require
frequent repairs.
Lamps shall be located in accordance with FMVSS/
CMVSS 108. NHTSA provides a resource online
that summarizes lamp location at http://www.nhtsa.
gov/cars/rules/standards/conspicuity/Trlrpstr.html.
Also see TMC RP 702C, Trailer Lamp and Reflector
Placement.
Incandescent lamps have been the most common
option for many years. However, light emitting diode
(LED) lighting offers the opportunity, when properly
installed, for the lighting system to last the life of the
trailer. Red LED lamps are often rated for 100,000
hours of steady operation and they offer significant
resistant to shock and vibration. LED lamps typically
draw about 1/10th the power of their incandescent
counterparts per specific function. With all of these
advantages, many fleets should give strong consideration to adopting these lights for their standard
lighting system to ensure maintenance free operation. See TMC RP 143, Light Emitting Diode (LED)
Technology.
K. Standard Size and Mounting
• Stop, Turn and Tail Lamps—Stop and tail, turn
and clearance, and combined lamps are to be
sealed assemblies.
• Clearance, Marker and Identification Lamps—
Experience has shown that mounting clearance, marker and identification type lamps
inside the upper rail or in a manner that
provides protection from physical damage
will reduce fleet maintenance costs. Efforts
shall be made to use lamp mounting locations
that meet the intent of the law and minimize
physical damage from tree branches or other
sources of physical damage. Consideration
for mounting of rear clearance, marker and
identification lamps should be given to prevent
physical damage to lights from dock seals.
Some of the new LED lighting products run
very cool and can be installed in extrusions
which prevent the dock seal from contacting
the surface of the lights (protecting both lamp
and dock seals). Supply wires for LED marker
lamps can be as small as 20 gauge and still
supply sufficient power to operate the lamps
properly.
©2013—TMC/ATA
• Lamps for Tank Trailers—Lamps should be
mounted in a protective box that eliminates
the direct spray of deicers/road salts on the
electrical connectors.
L. Reflective Tape and Reflex Reflectors
Reflectors shall be in accordance with in accordance with FMVSS/CMVSS 108. NHTSA provides
a resource online that summarizes lamp location at
http://www.nhtsa.gov/cars/rules/standards/conspicuity/Trlrpstr.html. Also see TMC RP 722A, Large
Vehicle Conspicuity Markings.
INSTALLATION BEST PRACTICES
The following recommendations will help ensure
proper installation and use of trailer lighting and
electrical system components:
1. Specify sealed connectors. This will extend
the life of the system and reduce the chance
for corrosion problems. Molded connectors
that once were the standard of the industry
are now becoming obsolete in favor of wellengineered hardshell connectors.
2. Use drip loops on electrical cables. Make sure
that excess cable and wire is installed properly
with the use of drip loops and attach the cable
to the vehicle chassis.
3. Use covers over connections to deflect spray.
An inexpensive cover or deflector can make
the installation much more robust.
4. Use electrical connector boots that can be
sealed with adhesives. If you must install a
connector in a spray environment use connector boots for extended life of connection
5. Be aware of exposing the system to fluids.
Fluids used for operation or cleaning can attack
lamps, connectors or wiring jackets. Ensure
that your specification considers these fluids
if used.
6. Use a dielectric grease to displace moisture
from connections (where possible). Use dielectric grease in areas that are recommended by
manufacture of the component (connector).
7. Mount all connections horizontally where possible. Horizontal mounting allow for the water or
spray to drain from the critical sealing area
8. Cover wires with both the proper insulation of
the individual wire and a secondary covering
that will provide more resistance to pinching or
cutting. Exposed wiring (copper) or individual
conductors is the fastest way to cause your
system to fail.
9. Review installation of wiring to lamps to ensure that the seals are not side loaded. The
harness should be designed so that there is
Proposed RP 704C(T) Ballot Version—
some extra length to assure that the connector
seals are not under tension.
10. Review lighting system installation to ensure
that no auxiliary devices like booms, lifts or
other devices interfere with the visibility of the
required lighting of the trailer prior to putting
trailer into service. Where this condition exists, supplemental lighting must be installed
to ensure visibility of the required devices.
11. Fleets are encouraged to perform a pre-delivery inspection of the lighting and harness
installation during pilot inspection of the
vehicle, component, and vehicle supplier(s)
should be present for this review.
REFERENCES
Regulations
USDOT National Highway Traffic Safety Administration (NHTSA), FMVSS 108. http://www.fmcsa.dot.
gov/rules-regulations/administration/fmcsr/fmcsrruletext.aspx?reg=r49CFR571.108
Transport Canada, CMVSS 108. http://www.tc.gc.
ca/eng/roadsafety/tp-tp13136-tr108-846.htm
Location of Lights
NHTSA and Transport Canada required lighting
locations tables and charts:
• Trucks and bodies— http://www.nhtsa.gov/
cars/rules/standards/conspicuity/TBMpstr.
html
• Trailers—http://www.nhtsa.gov/cars/rules/
standards/conspicuity/Trlrpstr.html
ASTM Standards
Available from ASTM International, 100 Barr Harbor
Drive, P.O. Box C700, West Conshohocken, PA
19428-2959, Tel: 610-832-9585, www.astm.org.
• ASTM B 117, Standard Method of Salt Spray
(Fog) Testing
SAE Recommended Practices
The following publications form a part of the specification to the extent specified herein. Unless otherwise
indicated, the latest revision of SAE publications
shall apply. Available from SAE International, 400
Commonwealth Drive, Warrendale, PA 15096-0001,
Tel: 877-606-7323 (inside USA and Canada) or 724776-4970 (outside USA), www.sae.org.
• SAE J163, Low Tension Wiring and Cable
Terminals and Splice Clips
• SAE J560, Primary and Auxiliary Seven Conductor Electrical Connector for Truck-Trailer
Jumper Cable
©2013—TMC/ATA
• SAE J1128, Low Voltage Primary Cable
• SAE J1455, Recommended Environmental
Practices for Electronic Equipment Design in
Heavy-Duty Vehicle Applications
• SAE J2139, Tests for Signal and Marking
Devices Used on Vehicles 2032 mm or more
in Overall Width
• SAE J2174, Heavy-Duty Wiring Systems for
Trailers 2032 mm or More in Width
• SAE J2202, Heavy-Duty Wiring Systems for
On-Highway Trucks
• SAE J2394, Seven Conductor Cable for ABS
Power—Truck and Bus
• SAE J2549, Single Conductor Cable for HeavyDuty Applications—Truck and Bus
• SAE J2577, Heavy Duty Lamp Electrical Connector Standard
TMC Recommended Practices
• TMC RP 110C, Low-Tension Cable for HeavyDuty Truck-Tractor Wiring Systems
• TMC RP 114B, Wiring Harness Protection
• TMC RP 137C, Antilock Electrical Supply From Tractors Through The SAE J560
Seven-Pin Connector
• TMC RP 141, TrailerABS Power Supply Requirements
• TMC RP 143, Light Emitting Diode (LED) Technology.
• TMC RP 153, Lamp to Connector Interface
Guidelines
• TMC RP 702C, Trailer Lamp and Reflector Placement
• RP 722A, Large Vehicle Conspicuity Markings.
TTMA Recommended Practices and Bulletins
Available from Truck Trailer Manufacturers Association, 8506 Wellington Rd. / Suite 101, Manassas, VA
20109, Tel: 703-549-3010, www.ttmanet.org.
• RP No. 9, Location of Lighting Devices
• TB No. 65, Wiring Diagram for Truck Trailers
• RP No. 90, Side Turn Signal Lamps for Long
Trailers
• RP No. 93, Trailer Conspicuity Systems
• RP No. 97, Trailer Antilock Braking System
Wiring
• RP No. 104, OEM Trailer Preparation for
Systems Using High Voltage Current Cable in
Trailer Bodies
• TB No. 111, Electrical System Maintenance
and Repair for Trailers Without Sealed Wiring
Harness Systems
• TB No. 119, Electrical Interface for Truck-Trailer
Interconnection
Proposed RP 704C(T) Ballot Version—
Recommended Practice
Proposed RP 1102A(T)
VMRS Various
TMC IN-SERVICE FUEL CONSUMPTION
TEST PROCEDURE—TYPE II
1. PREFACE
The following Recommended Practice is subject to
the Disclaimer at the front of TMC’s Recommended
Maintenance Practices Manual. Users are urged to
read the Disclaimer before considering adoption of
any portion of this Recommended Practice.
in moving to the temperature corrected fuel addition
method to measure fuel used is the use of the tanks
the vehicle was built with, fuel addition meters found
a commercial truck stops and longer runs that will
bring the temperature corrected method accuracy in
line with the weigh method.
1.1 PURPOSE AND SCOPE
This Recommended Practice (RP) provides a standardized test procedure for comparing the fuel consumption of two conditions of a single test vehicle or
of one test vehicle to another when it is not possible to
run the two or more test vehicles simultaneously. An
unchanging control vehicle is run in tandem with the
test vehicle(s) to provide reference fuel consumption
data. It is possible to control more than one test (i.e.,
having two or more test vehicles) with a single control
vehicle; however, if this is done additional care must
be taken in conducting tests largely because of separation of the vehicles on the roadway. Running two
test vehicles with the control vehicle in between the
two test vehicles is the simplest form of the multiple
test, single control vehicle approach.
NOTE: Also added to the procedure is a means of
including Diesel Exhaust Fluid (DEF) cost differences
in a manner similar to the way that fuel usage is
measured. To get a common basis for comparison
requires using cost in dollars for both fuel and DEF.
The details of these changes can be found below in
Sections 5.5.1 and 7.24.
The TMC Type II Test is especially suitable for testing components which require substantial time for
removal and replacement or modification, such as engines, transmissions, tag-axles, trailer aerodynamic
devices and cab sheet metal or cab aerodynamic
devices. This procedure may also be used for comparison of entire vehicles and/or for easy-to-change
components (those referenced in the TMC RP 1103
Type III procedure). TMC’s Type II procedure may
also be used for testing those components/vehicles
described in the Type III procedure. The test may
utilize fleet vehicles operating over representative
routes or at test facilities when available.
NOTE: Since its introduction, the Type II procedure
has recommended the portable tank weigh method
(called here after “the weigh method”) as the primary
method of measuring fuel used. In this revision, the
temperature corrected fuel addition method is recommended for those running tests at fleet locations
on the public highways. The major changes involved
NOTE: This revision does not mirror SAE J1321, Fuel
Consumption Test Procedure —Type II.
1.2 INTRODUCTION
For vehicles without after treatment that do not require
the use of DEF and do not have diesel particulate
filters (DPFs) that consume fuel during regeneration,
Type II test results may be given as a percent difference in fuel consumption between two test vehicles
or the difference in fuel consumption of one vehicle
for two different test conditions.
For vehicles using DEF and DPFs that use diesel
fuel for active regeneration of DPFs, the test results
can be presented as a percentage of difference of
the cost (in dollars for US testing) for fuel (to both
operate the vehicle and accomplish regeneration)
and the cost of DEF consumed.
The fuel measurement method is a key factor in
determining the overall test accuracy. The weigh
method of measuring fuel was the primary method
recommended for many years. For on highway testing by fleets and others it has been found that along
with using longer test runs of 140 miles (see below
) for on highway tests the temperature corrected
tank addition method will yield the measurement
accuracy required for the test while avoiding many
of the issues that must be managed when using the
weigh method.
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —
Issued 5/1982
Revised x/xxxx
The portable tank weigh method remains fully acceptable for use when conducting the test procedure; can be used on highway; though with careful
controls of fuel temperatures entering the engine it
remains possible to use test runs of 28-45 miles and
18 gallon tanks as referenced in earlier versions of
the procedure. However several testing facilities that
use the weigh method have moved to larger tanks
and/or return line fuel coolers as part of addressing
the maximum fuel temperature issues. (It should be
noted that this typically brings the need for forklifts
to remove and weigh the tanks.) The weigh method
is still well suited for tests utilizing professional test
facilities particularly where test tracks are available.
The weigh tank method has also been updated for
this version of the procedure. When using the tank
weigh method, again, it is critically important with
today’s engines that manufactures maximum fuel
temperature recommendations not be exceeded
because doing so will invoke electronic engine
controls that will effect fuel consumption and alter
test results.
If either the fuel weighing method using the recommendations found below or the temperature corrected
tank addition method with 140 mile minimum legs for
on highway testing is used, overall accuracy is best
and, based on test experience, will be within ± one
percent. (See Section 6, Test Accuracy.)
The following four basic rules must be applied to this
procedure to ensure test validity:
a. The test routes and cargo weight should be a
duty cycle representative of actual operation
or a documented duty cycle established for
comparative testing.
b. A single test is inconclusive regardless of the
results. A single test should be taken as an
indicator. Test results must be repeatable to
be valid. The ± one percent accuracy of this
test requires two results within a two-percent
window that are averaged together to get an
valid test result. Testing the same units twice
validates the result for those two units. A more
general answer requires testing more than one
pair of units. For example, if two pairs of tractors
with the same differences give the same result
in independent tests, the answer has much
broader use than does just one pair of trucks
tested twice. However, a trailer aerodynamic
device may be tested twice on the same vehicles
to get repeat data for valid results.
c. All test procedures or methods are accurate
within the prescribed limits. If the component
or system being tested by a given procedure
shows a degree of improvement which is
equal to or less than the accuracy limit of
the procedure, an additional number of tests
should be conducted to determine its true
value. If a number of such tests do not show
consistent results, then one must conclude
that the changes caused by the component or
vehicle system are less than can be measured
by the test procedure.
d. The more variables controlled, the more conclusive the results.
2. IDENTIFICATION
Sufficient information is to be recorded to identify
the vehicles under test and the route over which
the test is conducted. Minimum information required
is shown on Form 1: Type II Test Data (Vehicle
Identification).
3. TEST DEFINITIONS
Vehicles “C” and “T”—The vehicles being used
for test purposes are identified “C” and “T.” This
identification applies to the vehicles and associated
equipment, including the trailer, in the case of tractor/trailer combinations. Vehicle “C” is the control
and is not modified in any way during the entire test.
Control vehicle fuel and DEF (optional) consumption
is used only to generate control data. It is necessary
that Vehicle “C” be dedicated to the test and not used
for other purposes until the entire series of tests is
completed. The singular purpose of Vehicle “C” is to
monitor the test route, ambient conditions, and test
procedures for each test run. Vehicle “T” is the test
vehicle used to evaluate components. The procedure
also has the capability to test two vehicles, comparing one to the other. (See Sections 5.10 and 5.11
for explanation of the two-vehicle test.)
Test Run—A test run is a complete circuit of the
test route. A test run always starts and ends at a
common point. This may be accomplished by using
either a closed loop of highways or a single highway
with one half of the test run outbound, a turnaround
point, and one half of the test inbound, or a test track.
Each vehicle test run generates one data point. To
be usable, a test run must meet the constraints of
Section 5.7.
Data Point—A data point is the quantity of fuel consumed by a vehicle (either test or control) on a test
run. For vehicles with active DPF regeneration during
a test run, the fuel used for the active regeneration
must be subtracted from the total fuel used during the
run to determine the data point (i.e., before T over C
ratio is calculated — see below). If the fuel used for
the regeneration is not measured, the test run must
be considered invalid and must be repeated.
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —
T/C Ratio—A T/C ratio is the ratio of the quantity
of fuel consumed (data point) by the test vehicle to
the quantity of fuel consumed (data point) by the
control vehicle during one test run. Fuel to regenerate a DPF, if so equipped, is not used in T/C ratio
calculations. DEF usage though recorded for possible results calculations it does not enter into T/C
ratio calculations.
Baseline Segment—A baseline segment is composed of a minimum of three valid T/C ratios. A baseline segment establishes baseline fuel consumption
of the test vehicle or the first of two vehicles to be
tested. (See Sections 5.8, 5.9, 5.10, and Appendix
A, Sample Calculations, for further explanation.)
Test Segment—A test segment is also composed of
a minimum of three valid T/C ratios. A test segment
establishes the fuel consumption of the test vehicle
after modification or the fuel consumption of the
second of two vehicles tested. A valid test segment
must be compared to a valid baseline segment. (See
Sections 5.8, 5.9, 5.10, and Appendix A, Sample
Calculations, for further explanation.)
Complete Test—A complete test is composed of a
baseline segment and a test segment.
Single Valid Complete Test—A single, valid, complete test is comprised of a minimum of three valid test
runs meeting the criteria included in this procedure.
Without a second confirming test the work product
from a single test should not be referred to as an
answer until a second result confirms the first.
Valid Result or Answer—Two results inside a twopercent window should be averaged together to yield
an valid answer or result.
4. TEST and Test Vehicle PREPARATIONS
(Applicable to both Temperature Corrected and
Weigh Tank Fuel Measurements)
4.1 Vehicle Preparation
To minimize test variability, it is recommended that
all vehicles tested be similar in mechanical condition, representative of the fleet’s vehicles, and have
the same specifications (except in the case where
specification difference is the subject of the test):
a. Vehicles should have high-quality CB radios or
walkie-talkies in the cab of each test vehicle.
This will help the drivers: avoid mistakes that
would abort a test run, turn their lights, wipers, heating and air conditioning on and off
simultaneously, and warn each other of road
problems.
b. Each engine governor or electronically programmable drivetrain parameter, if set by the
engine, transmission or vehicle, must be set
in the same manner to manufacturer’s recommendation or the fleet’s standard unless
variation in these settings is a variable to be
tested. Verification of correct electronic engine/ programs must be accomplished. Driver
display devices generally display cruise set
points that eliminate analogue speedometer
errors and GPS can verify cruise speeds.
When there are questions about what device
is accurate for vehicle speeds GPS devices
are recommended as the one to consider
correct. If there are large variations between
GPS speeds and other indicated speeds it is
good practice to determine what is causing the
differences and it is very important if there is a
difference between the GPS indicated speed
and the device that sets the maximum speed
of the vehicle.
c. New air cleaner elements and fuel filters must
be installed. Installation of new air cleaner
elements can be waived if the vehicle’s inlet
restriction does not exceed 15 in-H20 (3.7
kPa). New fuel filters may be waived if less
than 5,000 miles have been accrued since a
previous change.
d. Each vehicle should be reasonably clean and
free of sheet metal dents, tears, or missing
body parts. Fiberglass hoods and fairings
should be intact.
e. Sliding fifth wheels must be set to give equal
trailer gap— measured back of cab to front
of trailer—unless the trailer gap is the test
parameter.
e. If two different tractor configurations are being tested and fifth wheel settings cannot be
adjusted for equal gap, then each fifth wheel
must be slid forward as far as possible with due
consideration for tractor-trailer clearance and
steer axle weight. Measure gap and record
on Form 1. In this situation the difference in
trailer gap becomes a specification difference
between the two test vehicles and is in this
case an appropriate part of the results.
f. On air-ride equipped vehicles, the air bag
heights must be set to provide equal vehicle
heights on identical equipment and set to the
manufacturer’s specifications if vehicles differ. If the vehicles differ the height difference
becomes a variable of the test.
g. Cab side window openings must be the same
in each vehicle (open or closed) at all times.
Opening or closing can be coordinated via CB
radio.
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —
h. Accessory loads for each vehicle must be as
consistent as possible, (e.g., by turning air conditioning off/on, defroster off/on, heat switch at
the same position, and lights on/off, etc.). Be
aware that on many vehicles the air conditioner
runs when the defroster is turned on. Use of
air conditioning must be coordinated between
drivers by CB radio. Additionally, the fan speed
selector on many vehicles differs in terms of
actual air movement from the vents. Attention
to air speed for selecting the fan speed setting
should not be overlooked. Higher air movement across the air conditioner evaporator
core will cause the air conditioner compressor
to run longer. Each time a driver changes an
accessory load in the cab or bunk, he or she
must communicate this change to the other
driver so that the loads may be equalized. In
the past it was recommended that these tests
be run without air conditioning. We now recommend that AC can be used if needed but care
should be taken to get cab temps as close as
is reasonably possible. Digital temperature
readouts in the cab and communication between drives can accomplish the equalization
of cab temperatures (this equalization is only
important when AC is used). History shows
that running defrosters in an equal manner is
more import than equal cab temperatures.
i. Trailer must be free of damage to exterior surfaces that would affect aerodynamic drag.
j. Truck/tractor must be checked for proper alignment. Trailer axle alignment should also be
checked for proper alignment, if applicable.
k. Each vehicle must be properly lubricated prior
to test. All fluid levels should be checked for
prescribed levels.
l. Temperature controlled fan drives must be
in the same operating mode throughout the
test. Observance of fan activity differences
between vehicles will assist in evaluating test
results. Measuring fan “on” time may be useful
for comparison. If vehicles are equipped with
different fan drives and/or fan drive controls
such differences become part of the differences being tested.
m.Cold tire pressures must be measured and
inflated to operator’s standard prior to running
each day.
n. A stall check should be performed on vehicles
equipped with automatic transmissions and
torque converters.
o. Exhaust system back pressure must be below
engine manufacturer’s maximum recommended limit and within 0.5 in-Hg (1.7 kPa)
between identical test vehicles. This can be
waived for vehicles with new exhaust systems
or for vehicles with less than 100,000 miles.
If the vehicle is equipped with a particulate
filter, a forced high-idle regeneration should
be completed. Also, the ash accumulators/
condition of the filters should be equivalent.
p. Proper brake adjustment is required.
q. When testing combination vehicles weighing
70,000 lbs. or more, where the test parameter
is the tractors or a test component on one of
the two identical tractors, the variance of the
total weight of the revenue freight and trailers
can be as much as 4,000 pounds or preferably
less than five percent difference between the
vehicles. The variance for lighter loads should
be reduced to maintain test truck performance
similarities. When comparing straight trucks,
the freight loaded in each truck should be equal.
If this is the case, load weights or axle weights
cannot be changed until the entire test has
been completed. If the load is removed and
replaced with another load, the axle weights
must be adjusted to be the same.
r. Fuel lines must be modified to accommodate
a weigh tank or to isolate one tank if the temperature corrected tank addition method is
used. The inside diameter of all lines, fittings,
coolers and quick coupled must be the same
size or larger than the original equipment
lines.
4.2 Test Route Selection
4.2.1. For Long-Haul Operations
a. Weigh Tank Fuel Measurement—A test route
representative of actual operation should be
selected for conducting the test of not less
than 28 miles (45 km) when using 18 gallon
tanks; longer test routes 45 miles (72.4 km)
are recommended if larger tanks are used.
When using the weigh tank fuel measurement
method, care must be taken to not exceed the
manufacturer’s recommendations regarding
maximum inlet fuel temperatures (see Section
4.8.4).
b. Temperature Corrected Fuel Measurement
Method—A test route representative of actual
operation should be selected for conducting
the test. The route should not be less than
140 miles (225km) where one tank of 50 to
150 gallons (568L) is used.
The route selected must have a high probability of
an uninterrupted test. Tests run on public highways
should be conducted in both directions on one
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —
highway or an “L” shaped routes is recommended.
(Record on Fig. 1, Test Data Form #1.)
4.2.2. For Other Operations
For other operations (e.g., pickup and delivery,
construction, transit buses, etc.), a representative
test route must be selected which will provide sufficient distance and time to consume a minimum of
20 percent of the tank capacity. The route selected
must have a high probability of an uninterrupted test.
(Record on Form #1.)
The 20 percent minimum of tank capacity has been
found to work on pickup and delivery (P&D) vocational
tests with 18 gallon weigh tanks. As of July 2013, insufficient data has been accumulated to demonstrate
the temperature corrected tank addition measurement
method for P&D tests. If temperature corrected fuel
addition tests for other operations are attempted,
TMC recommends that a minimum of 20 percent of
the capacity of a truck’s tank of 50-150 gal (568 L)
be consumed on a leg. (Record on Form #1.)
4.3. Vehicle Test Speeds
The test speeds selected should be representative
of average operation as determined by the operator
conducting the test and be within the capability of the
test vehicles. Vehicles are to be operated according to
the vehicle, engine, and transmission manufacturers’
recommendations (engine speeds and shift points).
If the test vehicles can be operated in more than one
transmission or differential ratio over any part of the
test route at the speed selected, a pre-determined
driving procedure must be specified. At no time during
the test cycle should one vehicle control the speed
or performance of the other vehicle; however, they
should be run at basically the same time in order to
experience the same ambient operating conditions.
(See Section 5.4.)
4.4. Vehicle Type and Configuration
Vehicles “C” and “T” are not required to be the same
configuration. However, it may require more test
runs to obtain three valid T/C ratios when extreme
differences in configuration exist between control and
test vehicles. and test vehicles. The more similar the
vehicles are in design the easier the test is to conduct.
All vehicles must be in proper operating condition as
determined by the operator conducting the test. (See
Section 7.7.) Vehicle “C” need not have the same
engine, driveline, axle ratio, or tire size as the test
vehicle. (Record on Form # 1.)
4.5. Cargo Weights
The cargo weights selected for the test should be
representative of fleet operations and be within the
capability of the vehicles under test. Equal gross
weights for Vehicles “C” and “T” are not necessary,
but are desirable. If two test vehicles are being
compared, the cargo weights must be the same.
Cargo weight must not change during a test unless
a change in weight is a factor being tested.
When testing tractor/trailer components to make the
test easier to run, it is recommended that the GVW
or GCW of both vehicles be with in five percent of
each other at the start of the first segment. And, no
weight is to be added or removed to either vehicle
during the test. When comparing tractors any weight
difference between the tractors becomes part of the
test. When testing trailers, straight trucks or other
vehicles (buses for example) the cargo weights must
be within one percent of each other and thus any
empty weight differences becomes part of the trailer,
straight truck or other vehicle test.
(Record measured weights of control and test vehicles on Form #1.)
4.6. Driver Selections
Drivers selected should be sufficiently skilled so that
test results are not affected by the driver’s technique
improvement during the test period. Drivers should
also have a strong motivation for unbiased results
and excellence of test procedure conduct.
4.7. Observers
Complex driving cycles require observers; simple
driving cycles typically do not require observers.
Observers, if used, must be unbiased.
4.8. Fuel Measuring
4.8.1. Temperature Corrected Tank Addition
Dispensing pumps normally used to fill trucks can be
used for this test with corrections to the fuel additions
made for temperature changed in the tank being
refilled. If this method is used, trucks with multiple
tanks must be modified to only draw fuel from one
tank. If “private” pumps that are not used for fuel
tax purposes are to be used for a test, calibration of
those pumps may be needed. Pumps used to sell fuel
at truck stops are almost always acceptable. Pumps
may have issues that can affect test result accuracy
at very low flow rates. If there are questions about
a pump, or as a test precaution, it is reasonable to
check whether the pump will repeatedly measure a
quart or liter of fuel. If after filling the same container
three times the results are with in two decimal places
on the read out, the pump is usable for testing.
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —
The “slave” system at fuel stop pumps can be an
issue. If the slave fuel line runs overhead, as opposed to underground, care may be needed (and
there may be things that can occur with under ground
slave systems that need attention). If there is doubt
about slave systems, dispensing one gallon from the
slave nozzle before filling test vehicles will eliminate
any influence of differences in residual fuel in slave
dispensers or crossover lines.
Temperature measurements are important and can
be taken with a multimeter that has the ability to
read thermocouples to plus or minus 0.1°F or C.
The thermocouple must be traversed through the
truck tank being used without touching the tank walls
and observing that the fuel temperature is constant
throughout the tank. The temperature is only taken
when the trucks tank used for the test is “full.” “Full” can
be determined in many ways. The simplest method
is to stop pumping when the fuel just touches and
is attached by surface tension to the lowest portion
of the tank’s fuel filler neck. If the test vehicles are
equipped with round tanks with filler necks in more
or less the same location from front to rear, the only
requirements are that the test vehicles be fueled at
the same pump with the steer axle of the truck in the
same location each time (chalk lines on the pavement work well for positioning the vehicles at the
fuel pump). If one or both of the two vehicles have
square or “D shaped” fuel tanks, the vehicles must
be leveled using a carpenter’s level or boards.
Test vehicles must be fueled at the same pump at the
end of a given test run. It is desirable that the same
pump be used for all test runs. It is more important that
one pump be used if the trucks are being returned to
a steer axle position on the ground (as marked with
a chalk line) as opposed to being leveled.
4.8.2. Portable Weigh Tank Method
This method of fuel consumption measurement
requires that a portable tank of at least 18 gal. (68.1
L) capacity be installed on each vehicle. Many organizations that run tests as a dedicated process
use tanks much larger than 18 gal (68.1L). This is
totally acceptable and may help alleviate high fuel
inlet temperature issues with some engines. Accordingly, it is recommended that fuel inlet temperature
be measured. If needed, a fuel return line cooler
should be used between the engine and the weigh
tank. Typically using larger tanks will require lifting
equipment such as forklifts along with appropriate procedures for operating lifting equipment and
weighing the larger tanks. Though a function of scale
accuracy, it is still recommended that 20 percent of
tank capacity be consumed by the engine during
runs used to obtain results.
The portable tanks must have provisions for both
supply and return of fuel. Good diesel tank design
practices must be followed for any portable tanks
used. All portable tanks used for a test should be of
the same design and capacity.
The fuel line connections to the portable tank must
be fitted with low-flow restriction, quick-disconnect
fittings to allow for removal without spillage. The
portable tank weigh method requires a good quality
scale that for 18 gal (68.1L) tanks is accurately calibrated in increments of 0.1 Ib. (45 g) or 1 oz. (28.4
g). (Use Form #2 for recording data.)
When reading a scale with graduations marked at
each ounce, it is a simple matter to interpolate to 1/4
oz. A deadweight of approximately 100 Ibs. (45.4 kg)
is required to check scale repeatability immediately
preceding each series of fuel tank weighings. (See
Section 7.4.) When larger tanks are used the accuracy requirements must be at a minimum scaled
to equal the requirements called out above for 18
gal (68.1L) tanks.
NOTE: It is strongly recommended that the portable
tanks selected have a high degree of mechanical
integrity. Temporary installation of an automobile fuel
tank is not recommended.
NOTE: A good scale for this purpose is Accu-Weight
Model 200 or equivalent, or Toledo Portable Digital
Scalebase Model 2096 used with Digital Indicator
8520 with 0.01 increments or equal.
4.8.3 Flow Meter Method
If vehicles are fitted with onboard flow meters, these
meters must be capable of temperature density
compensation and must be calibrated to a minimum
accuracy of ± one percent at flow rates consistent
with the vehicle being tested in the range of fuel
flow rates seen during the test which would basically be between the engines maximum fuel rates
and zero since vehicles often have fuel rates below
low idle when being partially “motored” in down hill
operation. But, if a set of meters can show accuracy
of within 0.5 percent when compared to the weigh
method or the temperature corrected tank addition
method results, using this set of meters should be
acceptable. Experience has shown that air — either
generated in or more likely released from the fuel
during the injection process — creates a challenge
for meters used in the fuel return to tank line. From
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time to time “day tank” systems with a single meter
have been proposed. The challenge here in addition
to meter accuracy is maintaining the same precise
level in the day tank (which is very doable in a test
cell with various devices but much more difficult in
a truck going down the road). Again, TMC has no
data on any metering system. TMC does not have a
way to say meters cannot be used, particularly if they
give the same results when compared to weighing
or temperature corrected tank additions. If meters
are used and there are questions, one check is to
move the meters between the two test vehicles and
see if the results remain the same. As of July 2013,
TMC has no data to support a minimum test route
length when fuel meters are used and has thus taken
a default position that the minimum test route length
should be the 140 miles as used in the temperature
corrected fuel addition method. (Use Form #2 for
recording data.) (See Section 6.2 for test accuracy
with fuel meters.)
4.8.3.1 Fuel Used for DPF Regeneration
Fuel used for DPF regeneration during a test run
must be subtracted from total fuel used on the run
before the T/C ratio is calculated. This fuel for trap
regeneration on test runs must be added back into
the test results. It is possible that historic data from
engine ECMs will give a better values for fuel used
to regenerate traps during the test (particularly if the
weigh method with its short test runs are used) This
requirement means that those conduction the test
must have access to and knowledge to operate engine
ECM software that monitors regeneration fuel used
both actively and from data stored historic standpoints.
For tests of components other than engines it may
be possible to run forced DPF regenerations before
each run (or to know when a regeneration will occur and run a parked regeneration before it occurs)
If this is done the fuel used for these regenerations
must not be included in the calculation of fuel used
and the T/C ratios.
If the scope of the test does not need to include the
quantity of fuel used by an active regeneration, then
if a regeneration occurs during a test run, the driver
should note that the run is invalid due to the regeneration. If the truck does not have a regeneration
indicator, a thermocouple can be installed after the
DPF with a read-out visible to the driver.
4.8.4 Fuel Temperatures
For all methods of fuel measurement, the fuel inlet
temperature to the engine should be kept below 160°F
(71°C) or below the engine manufacturer’s maximum
fuel inlet temperature. Fuel coolers can be used to
maintain the temperature below that value for the
portable tank method. Positioning the weigh tank in
an area of good air flow may be helpful.
4.8.5 Measuring DEF Use
and Impact on Test Results
For engines using DEF, the cost of DEF used must
can be added to the cost of fuel used to get a fair
comparison if the scope of the test requires this information. DEF can be measured by using a weigh
scale acceptable for U.S. Mail of or on the scale
used for the weigh tank method of measuring fuel
use. It is also acceptable to use the fleets historic
records of DEF use to get a cost to be combined
with the fuel used during the test (DEF costs are low
enough compared to fuel costs that any variation in
DEF use rates does not significantly affect the test.
However, ignoring the cost of DEF totally will yield
results with significant inaccuracies.) Since the answer for vehicles with DEF requires the use of two
items with different costs, the answer for the test
when DEF is involved is expressed as a percentage
of difference in dollars of fuel plus DEF used in the
two test vehicles.
4.9 Baseline Segment
Vehicles “C” and “T” must make sufficient test runs
to complete a baseline segment. (See Appendix A,
Sample Calculations.) After the baseline has been
established, modification is made to Vehicle “T.” No
change is made to Vehicle “C” for the duration of the
test. Vehicle “C” must remain the same vehicle, without change, and used for test purposes only, even if
modification to Vehicle “T” requires several weeks. If
trailers are used, the trailers and loads must be used
for test purposes only, or be set aside, unchanged
until the test is completed.
4.9 Test Segment
Vehicle “C” and modified or new Vehicle “T” must
make sufficient test runs to complete a segment.
(See Appendix A, Sample Calculations.)
5. TEST PROCEDURE
This test procedure is for use when testing a modification to a test vehicle or when comparing two vehicles
employing a switch of the complete test vehicle
between baseline segment and test segment. For
example, when comparing one test tractor to another,
the driver and trailer of the baseline segment vehicle
are the driver and trailer of the test segment vehicle.
The test segment is then compared to the baseline
segment. More than one test can be conducted and
several test vehicles can be operated at the same
time. When more than one test vehicle is run at the
same time, the control vehicle should be run between
the test vehicles and as near the middle as possible.
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Proposed RP 1102A(T) Ballot Version —
A single test is inconclusive, regardless of the results.
A single test should be taken as an indicator. Test
results must be repeatable to have validity.
A test consists of two segments— a baseline segment
and a test segment. Each segment is made up of a
minimum of three valid T/C ratios. (Test vehicle fuel
used divided by control vehicle fuel used.) Valid T/C
ratios must fit within a two-percent band. (See Appendix A, Sample Calculations.) The two-percent
band means that the lowest T/C ratio cannot be more
than two percent below the highest T/C ratio.
When not testing engines where DEF usage does
not enter into the results, and only one test vehicle
is used, a baseline segment is run. The vehicle is
then modified and a test segment is run as outlined in
Sections 4.1 through 4.9 and Sections 5.1 through
5.9. The comparison of the baseline T/C ratio and
test segment T/C ratio gives the test results. (See
Appendix A, Sample Calculations.) This does not
include DEF consumption.
If two complete vehicles are to be compared, the
Control Vehicle (C) and Test Vehicle One (T1) are
used in the baseline segment. The Control Vehicle
(C) and Test Vehicle Two (T2) are used in the test
segment. Both segments are run as outlined in
Sections 4.1 through 4.9 and 5.1 through 5.9. The
comparison of the baseline and test segments of the
vehicle(s) gives the test results. More than one test
vehicle can be run simultaneously, in which case the
divisor of the ratio is always the Control Vehicle (C).
(T1/C, T2/C, T3/C, etc.) (See Appendix A, Sample
Calculations.)
5.1 Pre-Test and Warm-Up Procedures
Vehicle “C” and “T” must follow the same pre-test
and warm-up procedures. Warm-up speeds should
be at or near test speeds. The time of warm-up must
not be less than one hour. Longer warm-up periods
may be required at colder temperatures. Warm-up
and driver familiarization with a test route can be accomplished at the same time. This test procedure is
structured to measure fuel consumption differences
of warmed-up vehicles.
A vehicle is considered to be sufficiently warmed
up when temperatures are near stabilized in tires,
hubs, bearings, differentials, and transmissions and
engine. Longer warm-up periods may be required
at colder temperatures.
• For the Weigh Tank Method—To prevent the
need for repeating warm-ups during test time
between runs including changing, tanks should
be limited to 20 minutes.
• For the Temperature Corrected Tank Addition
Method—The warm-up can be waived if the
test route is greater than 300 miles and if the
test trucks have been allowed to soak a period
of time within 10 percent of each other.
For all methods of fuel measurement, the warm-up
can be accomplished when traveling to the starting
point of the test if that run is 60 minutes or more.
5.2 Test Conditions
Record weather, road conditions, traffic conditions,
wind velocity, wind direction, temperature, humidity,
and barometric pressure for each test run. (Record
on Form #2. These data are not used in calculation
but are useful in evaluation of test results.
5.2.1 Wind Velocity
Wind velocity may be checked with an inexpensive
marine-type hand held wind indicator.(as available
from Edmund Scientific Co., Barrington, NJ, or Dwyer
Instrument, Inc., Michigan City, IN, or equivalent.)
5.2.2 Weather Data
Weather data may be obtained from a local airport
or other weather bureau services. By using portable
internet devices (with or without employing observers) more accurate weather data may be available
over the test route for each test run. In this procedure
weather data is used to understand results. Weather
may invalidate a test run because it forces a T/ C
ratio out of the two percent repeatability range. It is
possible that weather changes can affect entire sets
of segment data. If the baseline and test segments
are conducted under extreme temperature differences
or very different wind conditions the calculated results
could be significantly skewed.
5.2.3 Acceptable Weather Conditions
Valid tests can be run with ambient temperatures
between 36°F (2.2°C) and 105°F (40.5°C) with
maximum wind speeds of 25 mph with gusts to 30
mph. Valid tests may be run in rain as long as there
is no “ponding” of water on the roadway.
5.3 Fuel Dispensing
Vehicles must be fueled from the same dispenser
during the entire test to ensure consistent fuel grade
and quality. Specific gravity should be recorded at
start and end of each day as a minimum if the fuel
batch is questionable.
5.4 Start Procedures
When Vehicle “T” and Vehicle “C” are sufficiently
warmed up, and the drivers (and observers, when
required) are sufficiently familiar with the vehicles and
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Proposed RP 1102A(T) Ballot Version —
test route, they are brought to the test route stop/start
point and parked, with engines stopped.
• For the Weigh Tank Method—Pre-weighed
portable tanks are mounted on each vehicle
with the supply and return lines connected to
the engine.
• For the Temperature Corrected Tank Addition
Method— At the end of warm-up period, or prior
to the run if warm-up is waived, both vehicles
are filled to a predetermined point. Unless
the fuel in each test truck’s tank is known to
have the same heat value, the tanks must be
drained and refilled. They can be refilled with
the mixture of the fuel drained from both units.
When filling from commercial pumps, both
vehicles must use the same fuel pump with
the steer axle wheels in precisely the same
location. The parking surface should be level.
(See Section 4.8.1.) Fuel temperature must
be measured with tank full and recorded.
• For the Fuel Meter Measurement Method—
meters are read and recorded.
When all required data is recorded, Vehicle “T” is
dispatched on Test Run 1. This is accomplished by
starting the engine and immediately moving out; the
trip time starts when the wheels begin to roll. A 30-60
second idle period used for final equipment checks
is permissible, but, if used, must be the same for
each vehicle on each test run. The start time interval
between vehicles should be 30-120 seconds. This
will enhance the probability that both vehicles will be
exposed to the same ambient weather conditions. If
there is a horsepower difference, dispatch the highest
powered vehicle first. If vehicles are in visual contact,
it is essential that the following unit is out of (behind)
the turbulence caused by the leading unit. Example:
A speed of 55 mph requires that a following vehicle
be at least 13 seconds behind to be completely out
of the lead truck’s turbulence.
When testing vehicles of similar performance, the
lead driver must establish and maintain test (GPS)
speed, and the following driver must establish an
identical speed that will maintain the distance between vehicles. It is recommended, that the gap be
between 1/4-3/4 mile or 15-45 seconds. (See Section 5.4.3.) Maximizing the use of cruise control at
the same speed is the best method. If vehicles with
significant performance differences (e.g., 600 hp vs.
350 hp) are being tested to compare fuel economy,
the difference in separation on the highway will
change during the run.
The higher performance vehicle should be the first
vehicle out. The lower performance vehicle should be
second and initially start the run at the same speed as
the other vehicle. The cruise control for both vehicles
should be set at the same speed. A GPS device that
indicates 0.1 mph increments is helpful to initially set
the cruise control. After the cruise is set the distance
between the two vehicles may increase as the run
is conducted. The most important concern is that
each vehicle run the route within ± 0.5 percent of its
elapsed time. The time to complete the route does
not need to be the same for each vehicle.
5.4.1 For Vehicles With the Same Level
of Performance
Space maintenance measurement of vehicles in
visual contact is easily accomplished by observing
time between the two vehicles when each passes
the same stationary object along the route of travel.
A simple method is to measure time starting with
the shadow of an overpass passing over the lead
vehicle’s rear doors, and ending when the back of
the following vehicle passes under that same bridge.
Adjustments to following distance, if required, are
only made by the following vehicle and are only made
very slowly. Following distance of vehicles in visual
contact does not have to be the same on each test
run. Adjustments are only made when a closing or
opening of the measured distance is noted by the
following driver. The use of cruise control and/or
strict observance of test speed normally results in no
required speed adjustments once the vehicles are
up to test speed on the highway or interstate portion
of the test route.
GPS devices are the recommended method of
maintaining monitoring vehicle speed during the
test. If the exit from the highway portion causes
traffic-induced run time, the use of on-highway run
stop time is permissible providing the run stop time
is at the same physical location for each test run and
providing the test vehicle’s movements from run stop
time point to stop/start (weigh point) point is a vehicle
coast with engine at idle into a reset area or other
trip start/stop point and to equalize engine run time
when moving to the fuel pump when the temperature
tank addition fuel measurement is used. It maybe
helpful if each driver has a stop watch for engine idle
time accumulation to capture the time the vehicle is
stopped due to traffic around the refueling point or at
turnaround points on the course. If necessary the 60
second standard period may be increased somewhat
to another standard time period.
5.5 When the Vehicles Return
As each vehicle returns, it is stopped and the engine
speed reduced to idle for one minute minus total
stopped time at turn around or other predesignated
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Proposed RP 1102A(T) Ballot Version —
stops on the test course. The trip stop time is recorded
when the engine stops.
• For the Weigh Tank Method—Immediately after the engine is stopped, the quick disconnects
are uncoupled, fuel return first, and the portable tank is dismounted, weighed, recorded,
refilled, weighed, recorded, and remounted.
The quick disconnects are reconnected and the
vehicles are dispatched on Test Run 2 exactly
as they were the previous test run. If four or
more tanks are used, pre-weighed tanks can
be installed and the trucks started on the next
run, saving a considerable amount of time.
• For the Temperature Corrected Tank Addition
Method— Fuel used by each truck must be
measured at the end of each test run by recording the amount of fuel necessary to return
the level to the predetermined point in the
single fuel tank being used for the test. After
filling the tank to the predetermined point and
waiting for temperature stabilization, the fuel
temperature must be measured and recorded.
The temperature of the fuel should be checked
at least a minimum of three depths in the tank
while making sure that the temperature probe
does not touch the tank walls. A fuel volume
correction should be made using Form 1 and
Form 3. Odometer miles, times and other information are recorded on Form #1 (Vehicle
Identification).
• For the Fuel Meter Measurement Method—
Return readings are taken and recorded. Test
run elapsed time should be timed and recorded
by the person responsible for the conduct of
the test. Drivers (or observers, if required)
should time the amount of idle time that may
occur at turn around stop signs and advise
person recording so that it can be subtracted
from the 60 seconds of idle time to be taken at
end of each test run. This is usually not more
than 5-20 seconds and is subtracted from
total trip time since the engine at idle burns
an insignificant amount of fuel in that amount
of time. Drivers should not accelerate engine
above idle speed when stopped. Another
easy method of determining total trip time is
to have an observer measure and record the
maneuvering times at start, turn around, and
finish. The sum of these four times, subtracted
from total trip time, would be “highway only
time.” This should be done with a stop watch
and should be measured from the same points
each trip. See Form 3. Using this method will
usually result in fewer voided test runs due to
inconsistent times. However, if this alternate
method is used, it is very important that the
drivers start, stop, and make the turn around
exactly alike each test run. The elapsed test
run times of each vehicle with idle time removed on each test run must not vary ± 0.5
percent. Test runs that do not meet this time
constraint cannot be accepted and must be
repeated. This time constraint is a run-to-run
window of ± 0.5 percent on each vehicle and
is not a comparison of one vehicle’s time to
the other.
If preferred “rolling time” (i.e., time wheels
are turning) may be kept and used for this
constraint. “Rolling time” measurements may
require the use of observers. It should be
noted that “rolling time” and total time minus
idle time are the same information.
For long leg test runs of more than 50 miles
required by the temperature corrected tank
method and if used for other methods (large
weigh tanks or fuel meters) it is possible use
the time the vehicles are separated at the end
of the run with time on the course subtracted
instead of running time on the course. If done
the same ± 0.5 percent tolerance on the time
observed should be used. This method can
“save” long leg runs on public highways where
traffic conditions can effect travel times. If the
two(or more) vehicles being tested have significantly different exposure to traffic conditions
causing “rolling time” to be outside the ±0.5%
the required repeatability of the T/C fuel ratios
will not be met and the run excluded from
calculations do due to the T/C requirements
not being met.
The total time each vehicle is stopped between
test runs should be as short as possible and
limited to a maximum of 20 minutes. Best
practice is for times between runs to be the
same to ensure equal cool down.
• For the Weigh Tank Method—Due to the small
amount of fuel burned with small tanks (i.e.,
18 gal), the minimum recommended time between runs being the same is more important
because differences in cool down time can
affect vehicles enough to have a larger effect
of percentage of difference in fuel burned.
5.5.1 Measurement of DEF Consumed
DEF use is measured by filling the DEF tank on the
truck to a known level at the time the truck is fueled
before the first test run begins. This can be done by
establishing that the full mark supplied on the tank
is easily readable; marking a full mark on the tank
if there is not one or if factory marking is not clearly
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —10
readable or by use of a fabricated dipstick similar to
those that can be used for fuel full level measurement.
DEF may be added at the end of each test leg or it
may be added at the end of the last test run during
the day. The amount used is to be determined with
a scale acceptable for use with U.S. Mail. No more
than a standard 2.5-gallon store package should be
weighed on the scale and the weight recorded.
The DEF tank on the truck is filled to the full mark
established above and the DEF package is then
re-weighed and the weight recorded. Subtracting
the two readings will yield the DEF used. The DEF
used is then converted from "pounds of DEF used"
(9 lbs. per gallon) to “$/mile of DEF” used by working through Form 2-5: DEF Use Calculation Sheet.
The “$/mile DEF used” calculation has no impact on
the selection of acceptable test runs, it is only used
in the results calculation where cost of DEF used is
combined with the cost of fuel used to established
the difference on a $/mile basis for the two vehicles
being tested.
It is important to note significant changes in DEF
consumption during the test may indicate an issue that
will affect test results. It is also acceptable for tests
where DEF consumed will impact results — which
is typically when engines or complete vehicles are
the test component — to use the DEF consumed for
all miles from the place the vehicles are made ready
for test until the end of the testing day (which may be
returning to the place where the vehicles were stored
before the test day began). In this approach, all miles
and all DEF consumed for all Test Runs (both valid
and invalid), warm up runs (if any) and travel to return
the place the vehicles are being stored may be used
to determine DEF usage. It is also acceptable to use
historic records of the test vehicles in service use to
determine DEF usage. If historic records are used,
DEF consumption should be measured during at least
parts of the test to ensure that DEF usage during the
test is similar. Large deviations from historical DEF
rates or from manufacturers estimated DEF usage
rates may indicate a problem that could affect test
results and should be resolved.
5.5.2 Fuel Used to Regenerate DPFs for
T/C Ratio Calculations vs. Fuel Used
to Regen for Results Calculations
All miles and all fuel used for DPF regeneration or
“regen” can be used in the results of the test, but
fuel used for regens will be backed out of the fuel
additions used to determine valid fuel consumed T/C
ratios for Test Runs. For the results calculations if a
regen occurs in the last Test Segment, the impact of
the regen on fuel usage will be reduced by the inverse
of the ratio of miles to where the regen occurred to
total miles for the Test Run. (See Section 7.23 for
additional information.)
5.6 Driver/Observer Consistency
The driver of Vehicle “C” should drive that vehicle for
the complete test. The driver of “Vehicle “T” should
drive that vehicle for the complete test. After refueling occurs, repeat Sections 5.4 and 5.5. Record
weather, road and traffic conditions, wind velocity,
and wind direction. Observers should also remain
with their respective vehicles throughout the complete test since their instructions may influence driver
performance.
5.7 AT THE CONCLUSION OF EACH TEST RUN
At the conclusion of each test run, all data is recorded
and the next test run is started by repeating Sections
5.4 and 5.5.
• For the Weigh Tank Method—Time to complete a test run by each test vehicle minus
time stopped on the route or idle time must be
repeated within ±0.5 percent. For a run which
requires one hour to complete, repeatability
must be ±18 seconds.
• For Temperature Corrected Tank Addition
Method (and long legs of more than 50 miles
if fuel meters are used)—The separation time
between vehicles when they return from the
run may be used instead of running time. Fuel
consumption data should not be used from
runs which failed to repeat time within ±0.5
percent of other runs in the same segment
for the same vehicle. The use of runs that do
not repeat within ±0.5 percent, excluding time
stopped on the test route, will affect the accuracy of the results. The operational events
of these runs must be identical. The only
allowed variance is time spent at scheduled
stops. More complex test schedules may be
less tolerant of variations in stop-time.
5.7.1 Ton-Mile Per Gallon
If weight is the variable being tested, results should
be expressed in ton-miles-per gallon. A ton-mile-per
gallon is the amount of fuel expressed in gallons
required to move one ton one mile.
6. TEST ACCURACY
For the both the Weigh Tank Method and the Temperature Corrected Tank Addition Method, valid results are
considered — based on test experience with long-haul
test routes — to have an overall accuracy within ±
one percent (e.g., a six-percent measured difference
can range between five to seven percent).
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —11
The use of on-board meters has not been successfully
demonstrated during validation of this procedure. As
of July 2013, TMC does not have enough experience
with fuel meters to issue a statement regarding the
accuracy that can be obtained. Accuracy of tests will
depend on the meters’ accuracy and meter systems
will have variability in their accuracy. Meter systems
measuring and temperature correction for both supply and return to tank fuel are recommended. Such
a system would need an accuracy of ±0.5 percent
to be equal to the weigh method or the temperature
corrected fuel measurement technique method.
7. DEFINITIONS, CAUTIONARY NOTES
AND DISCUSSIONS
If test participants are extremely careful and pay attention to all details of the procedure, it has been found
that it is highly unusual that more than five test runs
are required to complete a segment. It has also been
found that, almost without exception, a procedural
error or a mechanical problem can be identified when
it is necessary delete a test run’s data. The following
information will help minimize such errors.
7.1 Test Preparation and Discussion
The test duration can extend over a period of three or
more days and test preparations should be supervised
by an experienced truck operator. Test drivers must
also possess a high degree of “truck sense” and a
strong desire to achieve quality data points. This
test may include but not require observers and/or
passengers. This test does require close attention
to detail in fueling, speed management, mid-point
vehicle-driver reassignment and recordkeeping.
7.2 Test Route
7.2.1. For the Weigh Tank Method
It has been determined during validation of the
procedure that the optimum long-haul test route is
one that starts and stops at a common point, has a
fueling point with easy access to the test route, and
has no traffic control lights. The turnaround should
be either the cloverleaf type or an off ramp with a
stop sign, an overhead (or underneath) crossover,
and an on ramp. Turnaround points with traffic control lights must be avoided. A test route that has had
mile (km) markers installed is recommended. For
other test routes (P&D, construction, transit buses,
off-highway, etc.) experience has shown that this
procedure is acceptable using the weigh tank method
for fuel measurement. However, care must be taken
in establishing routes and their inherent driving cycles
to ensure they are representative of the operating
parameters of the equipment under test. A duty cycle
must be established for the test that is representa-
tive of the in service work the vehicle dopes for the
results to be meaningful. P&D, construction, transit
buses, etc., routes will require observers to give
drivers specific directions so that the course will be
repeated in the same manner each time. For more
specific information about route development see
Sections 4.1.1 and 4.1.2.
For transit buses, the “Transit Coach Operating Profile
Duty Cycles” may be used.
NOTE: See Baseline Advanced Design Transit Coach
Specifications, Part II, paragraph 1.2 (17), Guideline
procurement document for new 30 and 40 ft (10.4
and 12.2 m) coach design. Published by the Urban
Mass Transportation Administration, a division of the
U.S. Department of Transportation.
7.2.2. For the Temperature Corrected Fuel
Measurement Technique
A minimum of a 140-mile course has been determined
to work very well. Limited access four or more lane
highways yield the best chance for successful test
runs that meet the test criteria for repeatability. Successful tests have been run on non-controlled access
four-lane highways and even on roadways that are
two lanes with low traffic density. It is possible (as
with the Type IV in-service procedure) to a run when
the unexpected happens during a test leg. To do
this requires that if something occurs with one truck
(slow moving traffic reducing speed of one truck for
example is common with 140 mile legs) that resultant
activity by one truck is mimicked as closely as possible by the other truck. For example if one truck is
slowed from test speed to 45 MPH for one half of a
mile, the other unrestrained truck slows similarly to
45 MPH for one half of a mile. This change requires
a change in route time keeping technique. The time
between vehicles technique when returning to the
fueling point, if there is a stop light or stop sign on the
course, the impact of any difference in time stopped
at the lights or signs must be removed from the time
between vehicles. It is recommended that two-lane
or four-lane, limited-access, divided highways be
used for test routes. Using interstate-type highways
as test routes will result in less data point divergence
and fewer invalid test runs. A direct comparison of
vehicles and drivers using both Type II Fuel Tests
and 250-mile long-haul tests have shown that fuel
consumption ratios can be within 0.25 percent. A
carrier should choose a route that represents the
route system used by that carrier, and a route that
they frequently use, so that a test result history can
be established. This could be invaluable in understanding test results variability.
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Proposed RP 1102A(T) Ballot Version —12
When selecting routes, test planners should avoid
the use of highways which feature multiple traffic
control devices. The use of CB radios or other communication devices to help the drivers equalize the
number of stops and accelerations will mitigate the
adverse effects of urban road travel. An ideal test
route is one that starts and stops within easy access
to an interstate or limited-access highway.
7.3 Trailer(s) and Weight Dedication
If trailers are used, the trailers matched to Vehicles
“C” and “T” should stay with their respective tractors
throughout the entire test. If this cannot be done
with the operator’s revenue generating equipment,
consideration should be given to renting trailers for
the duration of the series of test segments. Under
no circumstances should the trailers be exchanged
between Vehicles “C” and “T.” The use of revenue
cargo for test weight should be avoided to prevent
delay of freight or loss of costly test data due to an
unavoidable extension of the test period and/or cargo
delivery commitments.
7.4 SPEED, DURATION AND TEMPERATURE
STABILIZATION
Vehicles “C’’ and “T” should be operated at test speeds
for not less than one hour for warm-up before test
cycles are run to ensure that the vehicles approach
temperature stabilization of all components. Invalid
test runs may result if higher fuel consumption is
caused by temperature-induced frictional resistance
in one, but not all, of the vehicles used to conduct
the test. If fuel consumption during warm-up is being
tested, Vehicles “C” and “T” should not be operated
for a minimum of 12 hours prior to starting each
test run.
7.5. WEIGH TANK METHOD CONSIDERATIONS
Portable tanks must be weighed on the same portable
scales. See Section 4.7.1. The outside of the portable
fuel tanks should be wiped clean of dirt and fuel each
time they are weighed. Tanks must be disconnected
immediately after engines are shut off. The scale site
should be protected from winds.
NOTE: Scales must be checked with a known dead
weight of approximately 70-100 Ibs. (31.7 -45.4 kg)
before each series of readings.
Attention should be paid to the temporary fuel line
installation to prevent affecting test results. Very long
fuel lines required to mount portable tanks may affect
measured fuel use if the lines have combinations of
rise and fall relative to the ground that can at times
trap varying amounts of air in the fuel return line. The
amount of fuel in a 1/2-inch, inside diameter, 18-foot
long return line at the end of a test run can vary by as
much as 0.7 pounds. One way to eliminate this issue
is to place the quick disconnect coupler as close to
the engine as possible and weigh the return line with
the tank at the beginning and the end of each test
run if you think there is a repeatability issue.
When using the weigh tank method, It is strongly recommended that all drivers and observers (if observers are used) of Vehicles “C” and “T” be required to
practice driving the test route until run times become
repeatable. The average of the best repeatable run
times can be used to establish target times to meet
the ± 0.5 percent repeatability requirement.
7.6 TEMPERATURE CONTROLLED
FUEL TANK MEASUREMENT
TECHNIQUE CONSIDERATIONS
This method only requires one practice run of the
route before testing. Familiarity with grades, required
shifting, braking, speed maintenance, etc., will lead
to greater accuracy and repeatability. The goal during
practice is to establish consistent run times within
±0.5 percent. The more complex the driving cycle,
the more practice runs will be required to consistently
achieve the same run time ±0.5 percent.
7.7 MINIMIZING TEST VARIABILITY
To minimize test variability when driving the practice
run(s), it is recommended that each driver mentally
note the precise location on the test route where he
applies the brakes and for how long, where he shifts
gears, and where he accelerates and decelerates, and
where he engages or disengages the cruise control.
Each subsequent run should be an exact duplicate
of the previous run and no attempt to improve driving
should be made.
The use of stopwatches by observers and/or drivers to facilitate the measurement of time and speed
between mile (km) markers has been found to be a
valuable aid in meeting the time requirements of this
test procedure.
It has also been found useful to select mile (km)
marker checkpoints along the route and record the
time between markers, the time to negotiate a cloverleaf, and the time elapsed from interstate off-ramp to
on-ramp. The selected check-points should remain
the same for each test run. No attempt should be
made to compensate for a fast or slow elapsed time
between two previous checkpoints. GPS devices
are useful to accurately monitor test speed. This is
particularly important when testing complete vehicles
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Proposed RP 1102A(T) Ballot Version —13
or tractors when drivers are required to drive more
than one vehicle or tractor.
Also to minimize test variability, it is recommended
that all vehicles (“C” and “T”) being tested be in
similar mechanical condition and representative of
the operator’s vehicle(s) involved in the test. Additionally, (except in the case where this is the item
being evaluated):
a. Each engine ECM or electronic drivetrain be
set to manufacturer’s recommendation or the
operator’s standard. A review of historical and
active codes in engines, transmissions, brake
systems and vehicle data storage devices
should be completed. Vehicles with codes or
recorded incidents that could effect fuel consumption should be resolved before a vehicle
is used for fuel consumption testing.
b. New air cleaner element and new fuel filters
should be changed before testing begins.
Installation of new air cleaner element can
be waived if vehicles’ inlet restriction does
not exceed 15 inches H2O (3.7 kPa).
c. Each vehicle must be reasonably clean and free
of sheet metal dents, tears, or missing body
parts. Fiberglass hoods should be intact.
d. Cab side window openings should be the same
in each vehicle for the entire test. For transit
buses, all windows should stay in the same
position (open or closed) for entire test.
e. Accessory loads for each vehicle should be
as consistent as possible (for example, by
turning air conditioning off, defroster off, heat
switch at the same position, and lights on.)
f. Trailers should be free of damage to exterior
surfaces that would affect aerodynamic drag.
g. Truck/tractor alignment should be checked
and proper. Similarly, trailer axle alignment
should be checked and proper.
h. Each vehicle should be properly lubricated
prior to test. All fluid levels should be checked
and be at prescribed levels.
i. Temperature controlled fan drives should be
disabled to make the fan run continuously.
This should not be done when testing engines,
drivetrains or complete vehicles because the
additional horsepower demand of the fan may
not be the same for all test vehicles and thus
does not reflect a true difference in fuel use
when compared to normal fan operation in
normal freight hauling service.
j. Cold tire pressures should be measured and
inflated to the operator’s standard.
k. For vehicles with electronically controlled drivetrains, settings must be verified and should be
the same unless they are the subject of the
test.
l. A stall check should be run on vehicles
equipped with torque converters. Greatly differing stall check results should be understood
before vehicles are used for fuel consumption
testing.
m. Check that exhaust system back pressure
is below engine manufacturer’s maximum
recommended limit and within 0.5 inches Hg
(1.7 kPa) between test vehicle engines of the
same make and model.
n. Brakes properly adjusted. (Either disarm the
self-adjusting brake adjusters or check for
brake drag after each test run to assure that
a brake is not dragging.) The use of infrared
temperature measuring devices to monitor
wheel end and brake temperatures during
fueling stops is a good way to detect brake
issues that may affect test results.
o. Air dryer performance should be evaluated
and any unnecessary discharge of brake air
corrected.
p. Review data from finished runs and compare
not only the data needed for calculations but
any other information that may need corrective
action to make to results correct.
q. For engines equipped with particulate traps a
forced, zero speed, parked trap regeneration
should be conducted before the test is run.
After the regeneration ECM data should be
checked to see that the trap is ready for service
including but not limited to its ash loading vs.
the OEM’s maintenance requirements. Many
trucks will not have a regeneration during a
test segment to obtain three usable T/C ratios.
If regenerations do occur, the fuel used in the
regeneration must be subtracted from the fuel
burned to move the truck over the test route.
This is accomplished by obtaining fuel used
for regeneration from the engine ECM. Thus,
the appropriate service tools and an understanding of their use for extracting fuel used
in regeneration data is required. This data
is available for current engines; some 2007
through 2009 engines may not have this data
in their service tools. For 2007 to 2009 engines
enough data points data can be constructed
to allow running the test. However, in general,
avoiding the use of engines without regen fuel
use in their ECM data is recommended. An
alternative is to invalidate the run that had a
regen and continue the segment.
Like TMC’s Type IV Fuel Economy Test Procedure,
TMC’s Type II Procedure is dependent on data sup-
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Proposed RP 1102A(T) Ballot Version —14
plied by a manufacturer. That data is “the amount of
fuel used to regenerate particulate filters.” Though the
procedure described above is the preferred method,
an alternative method that does not require data from
a manufacturer is useful. Though a much longer procedure, experience indicates this alternative method
will achieve the desired results without the need for
the manufacturer’s regen fuel data.
This method requires running eight (8) runs of the two
vehicles. Typical “A over B ratios” are determined for
each run. Dashboard or service tool information as
to when a regen occurs, if available, is recorded. At
the end of eight runs, the A over B ratios are plotted
on a square grid format.
Runs with known regens from dash or service tool
data should have ratios move accordingly on the
plotted data. If A/B ratios with no known regens for
at least three runs are within the two-percent ratio
requirement of the primary test method above, and
the runs with known regens have ratios that move in
a direction and by an amount consistent with typical
amounts of fuel to execute a regen, then the cost
per mile costs using only fuel additions and DEF use
should be determined and the percentage of savings
for proposed new equipment calculated.
If, due to “bad luck,” there are not three runs in eight
where neither vehicle had a regen, then more runs
can be run. If there are five runs when neither vehicle
has regens and three do not meet the two-percent
ratio requirement, the answer/results should not be
calculated and work done to determine what is driving the ratios apart.
7.8 AT THE END OF WARM-UPS/TEST RUNS
At the end of each warm-up and at the end of each
test run, all vehicles must be checked for mechanical changes that would affect test results. Typical
checks would include:
a. Oil pressure and leaks
b. Coolant temperature and leaks
c. Exhaust gas temperature
d. Engine air filter restriction
e. Electrical load
f. Tire pressures
g. Brake dragging (i.e., temperature)
h. Observed ability to maintain selected test
speed
i. Transmission or differential leaks
j. Intake manifold pressure (turbocharger boost)
Drivers of Vehicles “C” and “T” should be interviewed
between test runs to ascertain any differences in the
apparent handling, power, and braking characteristics
of their respective vehicles. If changes occur during
the test runs of either the baseline segment or the
test segment, the test data should be discarded and
the test re-run after correction of the problem.
7.10 REPRODUCING ACTUAL CONDITIONS
In order to obtain results which may be considered
representative of actual service conditions, it is important to reproduce typical service conditions during
the test. This applies to load weights, routes, grades,
vehicle speeds, weather, wind conditions, drivers, etc.
For example, if the actual service vehicles generally
operate in a part of the country where hills exist over
a substantial portion of the routes, the test should
be conducted on similar terrain in order to obtain the
most representative results.
7.11 AERODYNAMIC DEVICE CONSIDERATIONS
Because of the special nature of aerodynamic drag
reduction equipment (e.g., deflectors, body fairings,
roof fairings, vortex stabilizers, etc.), comparison
tests between brands or types should not be run with
two trucks or vehicles. This means that when testing
these devices they should be installed and removed
from a single truck or vehicle. If comparative results
are required, additional test trucks are recommended
during any given test. The entire range of results may
be either higher or lower than average conditions
depending upon weather (wind velocity and direction)
on the days during which the tests were conducted.
To minimize the effects of high or low yaw angle wind
effects, a circular route or closed loop of highways is
recommended. If a circular route is not available, a
test route which includes equal distances of east-west
and north-south highway should be used.
Vehicles with very different aerodynamics may have
more difficulty in keeping ratios within the two percent window because of significant differences in
horsepower demand resulting from changes in wind
speed and direction. Keeping good weather records
are important when testing vehicles with different
aerodynamics. Should ratios within the two percent
window not be obtained when testing aerodynamic
devices, the test user may want to consider finding
a more “L” shaped course with as close as possible
the two “legs” of the “L” being of equal length.
7.12 ODOMETER/SPEEDOMETER ACCURACY
The accuracy of odometers and particularly speedometers of Vehicles “C” and “T” should be determined
during the warm-up test. Large amounts of time can
be consumed trying to get different vehicles to display the exact same vehicle speed information. The
use of consumer-grade GPS devices to set vehicle
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Proposed RP 1102A(T) Ballot Version —15
speeds can be a time-saver that actually yields better results than dash instruments. It is important to
ensure that critical vehicle speeds like max speed
and max cruise control speeds are the same on two
vehicles. If GPS devises are used to determine the
correct speed settings the readings on dash boards
may read differently. These dash board differences
should have no effect on test results if drivers control speeds with the GPS devices. However, these
differences in dash board speeds may well effect in
service fuel used because of the way they influence
fleet drivers to operate the vehicle and differences in
odometer accuracy can significantly effect calculated
MPG values if odometer miles are used for those
calculations.
7.13 Other Vehicle Temperature
Observations
The advent of infrared temperature measuring equipment brings a power tool that can help in ensuring truck
component changes are not introducing unwanted
variables into the test data. The observation of tire
temperatures from run to run on all wheel positions
can identify a tire problem that could be affecting the
data. Using tire temperatures may be a better alternative to checking tire pressure since many test runs
could be lost as a result of checking tires pressure,
causing a leak to develop.
Monitoring brake temperatures can locate problems
with self-adjusting brake adjusters or the wear in of
new brake components or recent adjustments that
can also create unwanted fuel use variability. (Though
issues caused by self-adjusting brake adjusters are
far less frequent today than when they were introduced in the 1970’s.)
Other areas that have from time to time been of
benefit when running two truck fuel tests are oil sump
or radiator tank temperatures finding malfunctioning
thermostats or oil cooler controls. If monitored much
of this data can be found in engine ECMs, but, issues
that can affect fuel test results can be smaller than
the limits set for warnings in ECMs.
7.14 Test Speed Selection
The maximum test speed or the electronically controlled ground speed (as set by cruise control) should
be representative of the fleet’s operation unless
speed is the variable being tested. Vehicles must
be operated within vehicle, engine and transmission
manufacturer’s recommendations (engine speeds
and shift points). If the test vehicles can be operated
in more than one transmission ratio over any part of
the test route, contact must be maintained between
the test drivers and the driving procedure must be
equalized accordingly. Note that different cruise
control logic may allow different overall average
speeds. Drivers should try to coordinate time spent
on cruise and allow for a faster lead vehicle if necessary. GPS units are easily available and affordable
for maintaining accurate speed control readings for
fleets and others conducting Type II tests.
7.15 Test Vehicle Specification
and Configuration
If a device or system is to be tested using only one
test vehicle, it is critical to ensure no changes other
than those required for the test component are made
to the test vehicle (no changes can be made to the
control vehicle). If a component of a combination
vehicle is being tested, all components of both
combination vehicles must be the same except the
component being tested. If two complete vehicles
are being compared, they need not be the same.
The differences in specifications or configurations
are what is being compared. TMC’s Type III Fuel
Economy Test Procedure (RP 1103) is more suitable
for this type of comparison.
7.16 TIRE CONSIDERATIONS
Tire engineering characteristics which significantly
affect rolling resistance are: tread compound, tread
depth and tread design aggressiveness. When
comparing two vehicles or the same components of
two combination vehicles (such as the tractors), the
tires should be identical—including tread depth. If
tires are being tested, the vehicles or components of
combination vehicles involved in the test comparison
must be identical in all respects—except the tires
being tested.
7.17 MILEAGE CONSIDERATIONS
Vehicles and tires should have a minimum of 2,500
miles of use before being used in a two-truck test
(10,000 miles are recommended). When testing new
vehicles with odometer mileage between 2,50010,000, the odometer readings of both vehicles
should be within 1,000 miles of each other. TMC
RP 1111A, Relationships Between Truck Components and Fuel Economy, indicates a possible five
percent efficiency gain from 0-50,000 miles during
engine/vehicle break-in.
7.18 Driver CONSIDERATIONS
Driver consistency is crucial to data point quality
and test result accuracy. The two drivers may use
different techniques, but they must each use their
own technique throughout the test without changes.
The drivers who start the test must complete the
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Proposed RP 1102A(T) Ballot Version —16
test. Driver substitution is not a good method. If it
is ever done, maximum cruise control usage of at
least 80 percent of the driving time is needed. Best
data point control is obtained when no attempt is
made to change a driver’s long-standing habits of
clutch use, braking, acceleration and deceleration
unless engine limiting software controls can be used
to limit the driver to certain driving characteristics. It
is bad practice to share fuel use values with drivers
because if one is consistently worse regarding fuel
use, that driver could change his driving habits to try
to improve and thus affect the test accuracy.
7.19 Observer CONSIDERATIONS
If observers are used, they should have a contributing function. Observers, if needed, should be assigned to a driver and assist that driver on every test
run. Observers should avoid distracting the driver.
Non-contributing passengers should be avoided to
minimize distraction and mistakes. Observers are
required are when complicated routes with muitiple
stops and varying desired speeds are performed.
7.20 Weather Measurement
Complete test summaries should include weather
conditions encountered during the conduct of the
test. This can be accomplished by using inexpensive,
hand-held instruments. Data recorded should include
temperature, wind speed, and direction, and relative
humidity. Instruments for measuring these conditions
are available from outdoor supply or marine stores.
Valid test runs come from repeatable fuel-use ratios.
Weather data is used to help explain invalid ratios or
changes in fuel used per mile. No data corrections
are made using weather data. An alternate method is
to collect data from local airports near the test route.
The National Weather Service is a good source for
this information.
7.21 TANK CONSIDERATIONS
7.21.1 For Temperature Corrected
Tank Addition Method
If the vehicle has more than one tank, only one fuel
tank should be used. The suggested fill location is
the highest repeatable location in the fill neck closest
to the center of the tank. Many anti-siphon devices
make accurate fills almost impossible and should be
removed if possible. Best method is to disconnect
and plug the lines connecting the second tank.
The fuel inlet restriction should still meet manufacturer's requirement utilizing the single source plumbing.
Tanks not used should be filled to a predetermined,
scribed mark on the fill tube and checked after each
test run to ensure that leakage to the other tank has
not occurred if plumbing disconnects are not made
and valves are used to stop flow between tanks, and
to ensure that tare weight is not altered by varying
amounts of fuel in the tanks. Both trucks should
operate from tanks on the same side of the truck to
minimize the effect of fuel island paving irregularities. Tanks used must be round or special action is
needed. Tanks used should have their filler necks
in the same location relative to the front and back
of the tank or the tank must be leveled front to back
by using jacks. The special action needed if square
tanks are used is to level the tanks for both front to
back and side to side to within 0.1° (electronic levels that do this are commonly available at building
supply stores).
The fuel tank on each truck that is to be used during
the test should be drained or pumped down to less
than 10 gallons and refilled with fuel from the same
pump/ and storage tank to ensure equal energy content. This can also be accomplished by intermixing
the fuel in the two test units before starting the test.
Note that if tanks have different fill cap locations, fore
and aft, fueling is best and most accurately conducted
from the same pump at the same fueling location
(e.g., a 200-mile loop out and return is better than a
200-mile leg at different locations.) Vehicle leveling
is the ideal method although spending time leveling
at the pump at busy truckstops is not realistic.
7.21.2 For Temperature Corrected Fuel Measurement Technique Tanks Addition Method
When measuring fuel temperature be careful not
to allow the probe or pick-up element to touch the
interior wall of the fuel tank since a false reading
may result. The actual fueling and topping-off to the
predetermined point should be done by only one
person to ensure consistency. If the fueling station is
not level, one person should direct the positioning of
each truck, taking care that the pump selected has the
best available pavement and each truck is positioned,
one at a time, on the exact same fore-and-aft track
with the front wheels at the same location for both
trucks. Trucks must be fueled one at a time. The first
unit fueled can be moved to any point in the lot and
parked with engine off. The second unit fueled will
be moved to a spot near the first.
7.21.3 Tank Leveling for the Temperature
Corrected Fuel Measurement Technique
When filler necks of round tanks are not in the same
location with respect to front-to-rear placement on two
vehicles, leveling tanks is desirable. It can be easily
accomplished with a level (see Section 5) and the
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use of the air-ride control on trucks so equipped, or
with 10-ton hydraulic jacks and two pre-cut 2x4 inch
boards. The jacks work because the leveling does not
require lifting the truck. If air-ride controls are used,
care must be taken to ensure the air suspension is
returned to the same height when fueling is completed.
Always position the level at the same locations on
the truck for both longitudinal and transverse measurements. Again if square tanks are used the tanks
must be leveled from front to rear and from side to
side using a level that reads to 0.1°.
7.21.4 Fueling for the Temperature Corrected Fuel
Measurement Technique
To avoid false fuel level readings, the best point to
use is the point at which the fuel just touches the inner
filler neck. Anti-siphon devices should also be filled to
the uppermost fill orifice, if used. Ensure the device
sleeve is indexed to the same position used in initial
fill. The best thing to do with antsiphon devices is to
remove them to ensure that the pump will measure
small amounts of fuel accurately.
7.21.5 Fuel Temperature Stabilization and
Correction for the Temperature Corrected
Fuel Measurement Technique
Fuel temperature in on-board storage tanks is higher
and varies considerably with the engine type and
make, run length, tank size, ambient temperature,
wind and the time the truck is parked.
The fuel temperature correction shown in Form 1?:
“Temperature Correction for Type II Fuel Test Run”
is based on the following: The liquid capacity of the
tanks is known by either reading it from the tank or
calculating it from measurements taken with the tank
full of fuel. The volume of the tank does not change
significantly with the temperature experienced. (That
is the physical dimensions of the tank do not change
enough due to the coefficient of thermal expansion of
the metal from which the tank is made to significantly
change test results).
The critical value that does change with temperature
is the amount of energy in the tank (i.e., the weight
of the fuel in the tank) when it is filled to the same
level but with different fuel temperatures inside the
tank. This difference in fuel weight or energy in the
tank with different fuel temperatures is what needs
correction.
The method of correcting the difference in fuel temperature is determining the amount of energy in the
tank. Though this is best explained using an example,
it is important to remember that if the temperature
in the tank increases during a run, the difference is
added to the pump reading, and if the temperature
in the tank decreases the change is subtracted from
the pump readings. (In the calculation, this is done
by adding a negative number.) For example, assume
a tank has a liquid usuable capacity of 100 gallons.
A test run is made that uses 50 gallons. At the start
of the run, the temperature is 75°F. At the end of the
run, the temperature is 95° F. Thus, (95 - 75) x 100
x 0.0005 = 1. The temperature corrected addition is
51.0 gallons (50.0 + 1.00 = 51.0). Thus, 51.0 gallons is the amount of fuel that would be used for all
calculations for this vehicle on this run.
7.22 RIDE /FIFTH WHEEL HEIGHT
Ride height or fifth wheel height should be measured
and documented for both vehicles and any changes
duly noted during the test procedure.
7.23 Active Regeneration Capability
When testing 2007 and later model year engines
equipped with catalytic converters that have active
regeneration capability, the fuel used to regenerate
must be made available by the engine manufacturers.
The engine manufacturer’s software providing engine
data needs to show each time the particulate trap is
actively regenerated. The fuel used for regeneration
must be backed out of the calculation of T/C ratios
that determine the acceptability of a test run’s data.
The fuel used for regeneration must be worked back
into the results calculation.
7.23.1. Forced Regeneration
For vehicles equipped with DPFs, a zero ground
speed forced regeneration of the DPF is recommended before testing. After the forced regeneration, the
trap’s DPF back pressure should be in then acceptable
range or DPF maintenance is likely required.
7.23.2 Fuel Used for Regeneration in Valid Ratio
Determination vs. Fuel Use for Regeneration In
Test Results
These two values result from the need to “back out”
the fuel used for regeneration to determine valid
test runs based on ratios of fuel burned — all while
minimizing any negative impact on accuracy of fuel
used to accomplish regeneration in an “in service”
situation. Since the regeneration process is continuous, taking regeneration fuel use out would result
in invalid ratios that artificially make the process
non-continuous. An alternative would have been to
force a regeneration before the beginning of a test
run. This was not done because it would take away
any advantage for a system that is designed to use
less fuel in the regeneration process. To further
equalize two systems regenerations occurring in the
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Proposed RP 1102A(T) Ballot Version —18
last Test Run, a series comprising a valid test will be
“adjusted.” If a regeneration occurs during the last
Test Run of a valid test by using the inverse of miles
run during the Test Run to the point regeneration
occurs to total miles in the last Test Run, the impact
on results of a regeneration that will run the vehicle
to a mileage accumulation well beyond the end test
is mitigated.
7.24. DEF Usage
When the component being tested is engines and
when testing 2010 and later model year engines that
use DEF for treating the engines exhaust stream,
the amount of DEF used must be measured and
the impact on the cost of the DEF included in the
results calculation. If the component is tested does
not use a 2010 and later model year engine, the DEF
measurement does not get included in the calculations. However, it is recommended that DEF use
be measured even though it is not included in the
results because significant changes in DEF usage
can indicate an issue that may affect test results. If a
significant change in DEF usage is noted an investigation into why the change occurred is recommended.
DEF should be measured for the full day's runs and
then calculated into cost per mile utilizing the day's
mileage due to the small volume of DEF consumed
for each individual run.
7.24.1 Common Term
When testing engines two dissimilar fluids make up
the result for a test of an engine using DEF, a common term is needed for the results calculation. The
term used for this RP is “$ per mile” or “$/mile.” Both
fuel used and DEF used will be expressed in “$/mile”
for the results calculation.
7.24.2 Cost of DEF and Fuel Used in Test Results
When testing engines or any time a result is to be
expressed in terms of cost per mile, the cost per unit
(i.e., cost per gallon or cost per pound) of both fuel
and DEF is needed for the results calculation. Though
those costs could be obtained from costs experienced
during the test, it would seem to make more sense
for the fleet or other organization conducting the test
to set these costs in line with what the equipment
tested will realize when in revenue service.
7.26 Space Between Vehicles
It is essential that the trailing vehicle is out of (behind)
the turbulence caused by the leading unit. Example:
If the leading vehicle is maintaining a speed of 55
MPH, the trailing vehicle must travel at least 13
seconds behind the lead vehicle to be completely
out of the lead vehicle’s turbulence. Measuring the
distance between the lead and trailing vehicles can
be done visually and is easily accomplished by
observing time difference between the two vehicles
when each passes the same stationary point along
the route of travel.
A simple method is to measure time starting with
the shadow of an overpass passing over the lead
vehicle’s rear doors, and ending when the trailing
vehicle’s windshield passes under that same bridge.
Adjustments to following distance, if required, are only
made by the following vehicle and are only made very
slowly. The following distance of vehicles in visual
contact does not have to be the same on each test
run. Adjustments are only made when a closing or
opening of the measured distance is noted by the
following driver.
The use of cruise control and/ or strict observance
of test speed normally eliminates the need for speed
adjustments once the vehicles are up to test speed on
the highway or interstate portion of the test route. The
use of cruise control reduces data point differences
variables of the data and is recommended. Typically,
a distance of 0.5 to 1.5 miles is set. In cases where
the following truck is moving at a faster rate even
with identical cruise set speeds, the following truck
is allowed to become the leading truck. Adjustments
in speed to maintain the gap is not preferred due to
inability for repeatability between test runs.
When evaluating different drivetrain ratios, horsepower ratings or gross vehicle weight differences,
the distance between the test vehicles may widen
when traveling through elevation changes. The lead
truck should be the one able to maintain the highest
average ground speed and the gap between the
vehicles may increase up to five minutes. If the gap
ever exceeds five minutes on either leg, the vehicles
have too much difference in performance to use this
procedure. This gap should be timed both at the
mid-point and at the end of the test run. The time differences should be given included in the test results.
Large vehicle speed capability variables should not
be tested using this method.
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —19
APPENDIX A—SAMPLE CALCULATIONS
A.1 DERIVATION OF BASELINE DATA
A 1.1 Baseline Segment
A. Sample Collection:
Fuel Consumed,
Test Run
Number
1
2
3
Fuel Consumed,
Ib. or kg, Test
Vehicle (Data Point)
Ib. or kg, Control
Vehicle (Data Point)
78.94
79.41
77.50
T/C Ratio
68.04
66.84
66.84
1.1602
1.1881
1.1595
Check: T/C values must be within 2% (Use 0.98 as a multiplier for this purpose):
B. After three test runs, calculate minimum acceptable T/C ratio :
Highest T/C ratio x 0.98 = minimum acceptable T/C ratio
1.1881 X 0.98 = 1.1643
The T/C ratios derived by test runs #1 and #3 are less than the minimum acceptable T/C ratio calculated above. Therefore, additional baseline data are required. This comparative test to assure
T/C ratios within 2% should be made after the third test run and then after each succeeding test
run that is required. When three test runs are repeated within 2% of each other, as checked in Step
B, the baseline segment is complete. In this example, an additional test run is required as shown
below.
Test Run
Number
1
2
3
4
Fuel Consumed,
Ib. or kg, Test
Vehicle (Data Point)
78.94
79.41
77.50
78.54
Fuel Consumed,
Ib. or kg, Control
Vehicle (Data Point)
68.04
66.84
66.84
67.84
T/C Ratio
1.1602
1.1881
1.1595
1.1577
C.
If required, recalculate minimum acceptable T/C ratio after four test runs as follows:
Because there are three T/C ratios greater than the minimum acceptable T/C ratio as determined
by calculation C.2, the requirement that three test runs fall within a 2% band has been met and the
baseline segment is complete.
C.1 Highest T/C ratio x 0.98 = minimum acceptable T/C ratio
1.1881 x 0.98= 1.1643
C.2 Second highest T/C ratio x 0.98 = minimum acceptable T/C ratio
1.1602 x 0.98 = 1.1370
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —20
APPENDIX A—SAMPLE CALCULATIONS (continued)
Test runs #1 and #3 were valid when tested by comparison with test run #4. Therefore, run #2 is
considered faulty and is deleted as part of the baseline segment. Since runs #1, #3, and #4 meet
the 2% requirement, a #5 test run is not required. The same procedure shown at Steps A and B is
repeated as in C.
D. If a fifth test is needed for three valid T/C ratios, the determination of those runs is done as follows:
D.1 Highest T/C ratio x 0.98 = minimum acceptable T/C ratio
D.2 Second highest T/C ratio x 0.98 = minimum acceptable T/C ratio
D.3 Third highest T/C ratio x 0.98 = minimum acceptable T/C ratio
NOTE: If test participants are extremely careful and pay attention to all details of the procedure,
it has been found that it is highly unusual that more than five test runs are required to complete a
segment. It has also been found that, almost without exception, a procedural error or a mechanical
problem can be identified when it is necessary to delete a test run.
The test segment may now be started.
A.1.2 Test Segment
Make similar calculations as in the baseline segment. (Typical test segment results are shown in paragraph
A2.2.)
A.2 CALCULATION OF RESULTS
After finishing a baseline segment and a test segment, calculate the result. That is, compare the baseline
segment, performed before the component change was made to the truck, to the test segment, performed
after
the change. Each segment was run until three T/C ratios of fuel consumption were obtained which met the
2% test. For calculating the results, we must now compare them.
A.2.1 Baseline Segment T/C Ratios
Test Run #1
Test Run #3
Test Run #4
Average
1.1602
1.1595
1.1577
3.4774
÷
3 = 1.1591
÷
3 = 1.0992
A2.2 Test Segment T/C Ratios (See A1.2)
Test Run #2
Test Run #3
Test Run #4
Average
1.0959
1.1080
1.0936
3.2975
The T/C ratios derived in each segment compare th fuel consumption of the test vehicle (T) to the control
vehicle (C). It is by comparing these ratios, that we derive the percentage improvement (positive or negative)
between the baseline segment (before the component change) and the test segment (after the component
change).
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —21
APPENDIX A—SAMPLE CALCULATIONS (continued)
A2.3 Percent Fuel Saved
= (Avg. Baseline T/C - Avg. Test T/C) ÷ (Avg. Baseline T/C)
= (1.1591 - 1.0992) ÷ 1.1591
= (0.0517 x 100) = 5.17% Fuel Saved
A2.4 Percent Improvement
= (Avg. Baseline T/C - Avg. Test T/C) ÷ Avg. Test T/C
= (1.1591 - 1.0992) ÷ 1.0992
= (0.0545 x 100) = 5.45% improvement
A.3 MPG (km/L) CONVERSION
The preferred method of expressing the result of a test is as a percent of fuel saved, as described in paragraph A2.3. If it is desired to have fuel consumption stated in mpg (km/L), it must be emphasized that these
values apply to specific test conditions only. This section of the procedure describes how to state the results
in consistent mpg (km/L) values.
Fuel consumption of the control vehicle is used, in an arbitrary role, in this calculation. For reasons of consistency, so that the resulting mpg (km/L) values can be compared with each other, it is important that the
same control vehicle mpg (km/L) value be used to derive all test vehicles’ mpg (km/L) values. Two ways of
calculating this representative control vehicle mpg (km/L) are shown and the choice between them is not
important. It is important that the precaution be followed of using only one representative control vehicle
(including driver) mpg (km/L) value to calculate all mpg (km/L) values which might be compared with each
other.
The fuel specific weight of the actual test fuel should be determined and used for this calculation. As an
alternative, a value of 7.05 Ib/gal (0.84 kg/L) for No. 2 diesel and 6.0 Ib/gal (0.72 kg/L) for gasoline may be
used.
A3.1 Representative Control Vehicle mpg (km/L)
The control vehicle representative mpg (km/L) can be obtained from valid fuel consumption for one day or
from the valid fuel consumption for every time that control vehicle was used.* For this example, the baseline
segment valid runs will be used.
68.04
66.84
67.84
202.72 Ibs. for 3 runs
Run #1
Run #3
Run #4
202.79 Ibs ÷ 7.05 Ibs/gal = 28.75 gal
(91.95 kg ÷ 0.85 kg/L = 108.17 L) **
50 miles x 3 runs = 150 miles
(80.5 km x 3 runs = 241.4 km) ***
150 miles ÷ 28.75 gal = 5.22 miles/gal ***
(241.4 km ÷ 108.17 L = 2.23 km/L)
*5.22 mpg (2.23 km/L) has been established as representative of this control vehicle recognizing that
tests run on other days under different weather conditions will result in a different mpg (km / L) value
for the control.
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —22
APPENDIX A—SAMPLE CALCULATIONS (continued)
vehicle. However, for other tests where this control vehicle is used for the purpose of converting to mpg
(km/L) the 5.22 mpg (2.23 km/L) must be used as the representative value if a valid mpg (km/L) conversion is to be made. If a new representative value is used, all previous mpg (km/L) improvements must
be recalculated using the new representative value.
** To convert Ib to kg, multiply Ib by 0.4536.
***To convert mi. to km, multiply miles by 1.6093.
A.3.2 Test Vehicle Baseline mpg (km/L)
Control vehicle representative mpg (km/L) ÷ Avg. Baseline T/C Ratio
5.22 mpg ÷ 1.1591 = 4.50 mpg
(2.23 km/L ÷ 1.1591 = 1.92 km/L)
Test Vehicle Test mpg (km/L)
Control vehicle representative mpg (km/L) ÷ Avg. Test T/C Ratio
5.22 mpg ÷ 1.0992 = 4.75 mpg
(2.23 km/L ÷ 1.0992 = 2.03 km/L)
A.3.3 Improvement in mpg (km/L)
Test – Baseline
4.75 – 4.50 = 0.25 mpg improvement
(2.02 –1.92 = 0.10 km/L improvement)
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —23
FORM 1: TYPE II TEST DATA (VEHICLE IDENTIFICATION)
Power Unit
Fleet
Date
Test #
Control Vehicle
Test Vehicle
Unit Number
Make
Model
Year
Number of Axles
Number of Drive Axles
Engine Make/Model
Governed Speed @ No Load (High Idle)
RPM
RPM
Rated Power (bhp)
hp (kw)
hp (kw)
Rated Speed
RPM
RPM
Peak Torque
Ib-ft
Ib-ft
Peak Torque Speed
RPM
RPM
Geared For
mph (km/h)
mph (km/h)
at
RPM
at
RPM
in
gear
in
gear
Transmission Make/Model
Differential Make/Model
Differential Ratio
Tire Size/Type/Make/Model
/
Tire Pressure (Cold)
/
/
/
psi (kPa)
psi (kPa)
in (mm)
in (mm)
5th Wheel Setting (express in
in (mm) the distance 5th wheel
fulcrum is ahead or behind the
center line of bogie)
Note: In areas where two units are shown [i.e., hp (kw)], circle the unit used.
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —24
FORM 1: TYPE II TEST DATA (VEHICLE IDENTIFICATION) (Continued)
Trailer/Body
Fleet
Date
Test #
Control Vehicle
Test Vehicle
Unit Number
Make
Model
Year
Type (Van, Flatbed, Tank, Etc.)
Type of Side
Type of Corner
Height
Length
Tire Size/Type/Make/Model
Tire Pressure (Cold)
/
/
/
/
psi (kPa)
psi (kPa)
in (mm)
in (mm)
Number of Axles on Trailer(s)
G.V.W. (Measured on Scale)
Kingpin Setting
Cab-to-Trailer Gap
Width
Aerodynamic Device
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —25
FORM 1: TYPE II TEST DATA (VEHICLE IDENTIFICATION) (Continued)
Devices, Components, or Systems That Are Incorporated
into Control and Test Vehicle Specifications
Fleet
Date
Test #
Control Vehicle
No
Yes
Test Vehicle
Type
Radiator Shutters (on-off or modulating)
Engine Cooling Fan Sys. (Describe below—A)
Aerodynamic Device (Describe below—B)
Engine Oil
Transmission Lube
Differential Lube
Fuel Heater
Oil Cooler
Tag Axle
Air Lift Axle(s)
Low Back-Pressure Exhaust System
Other:
A
/
B
/
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —26
No
Yes
Type
FORM 1: TYPE II TEST DATA (VEHICLE IDENTIFICATION) (Continued)
Fleet
Date
Test #
Detailed Description of Vehicle, Component, or System Modification Being Tested:
Length of Test Route from Start to Stop Point:
miles (km)
Test Route: (Describe in detail number of lanes; type of road surface; type of turnarounds; type, if
any, of traffic control devices; type of terrain, hills, cuts, curves; special driving instructions; etc.)
Driver(s) Interview
Handling, Power, and Braking Characteristics of Vehicle(s) during Test (see paragraph 7.5):
Control Vehicle
Test Vehicle
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —27
FORM 2-1: TYPE II—FUEL ECONOMY TEST DATA
BASELINE SEGMENT OF THE CONTROL VEHICLE
Type II Test—Portable Fuel Tank Weighing Method or Fuel Flow Meter Method
Fleet
Control Tractor #
Control Trailer #
Driver
Observer
Test #
Date
Test Speed
Route
Test Run #1
Scale Repeatability Check Weight
Fuel Weight/Fuel Meter Reading/Pump Corrected1
Odometer
Time
Start
Finish
Fuel Used
Ib/gal kg/L (circle one)
Time from Start to Finish
h
m
s
Subtract Vehicle Stopped Time
h
m
s
Vehicle Running Time*
h
m
s
Test Run #2
Scale Repeatability Check Weight
Fuel Weight/Fuel Meter Reading/Pump Corrected1
Odometer
Time
Start
Finish
Fuel Used
Ib/gal kg/L (circle one)
Time from Start to Finish
h
m
s
Subtract Vehicle Stopped Time
h
m
s
Vehicle Running Time*
h
m
s
Test Run #3
Scale Repeatability Check Weight
Fuel Weight/Fuel Meter Reading/Pump Corrected1
Odometer
Time
Start
Finish
Fuel Used
Ib/gal kg/L (circle one)
Time from Start to Finish
h
m
s
Subtract Vehicle Stopped Time
h
m
s
Vehicle Running Time*
h
m
s
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —28
FORM 2-1: TYPE II—FUEL ECONOMY TEST DATA (Continued)
Test Run #4
Scale Repeatability Check Weight
Fuel Weight/Fuel Meter Reading/Pump Corrected1
Odometer
Time
Start
Finish
Fuel Used
Ib/gal kg/L (circle one)
Time from Start to Finish
h
m
s
Subtract Vehicle Stopped Time
h
m
s
Vehicle Running Time*
h
m
s
Test Run #5
Scale Repeatability Check Weight
Fuel Weight/Fuel Meter Reading/Pump Corrected1
Odometer
Time
Start
Finish
Fuel Used
Ib/gal kg/L (circle one)
Time from Start to Finish
h
m
s
Subtract Vehicle Stopped Time
h
m
s
Vehicle Running Time*
h
m
s
Control Vehicle MPG Calculation
Total Fuel Used
Total Fuel Used Ib/gal
Total Miles (km) Run
Miles (km) of Run
or
kg/L**
Ib/gal
÷
÷
kg/L (circle one)
Time
÷***
=
gal (L) used =
h =
miles/h (km/h)
Weather:
Temperature
Humidity
h
m
gal (L)
miles/gal (km/L)
Barometric
Pressure
Wind Speed
s
Wind
Direction
Run #1
Run #2
Run #3
Run #4
Run #5
Total DEF Used for All Runs This Day _______________gal / L (circle one) (See Footnote 2)
* Running time must repeat within ±18 seconds for a one hour run or ± 0.5% of the time required to complete the test
run or run data point must not be used. See paragraphs 3.2, 3.3, 5.5, and 5.9.
** If a fuel meter is used, record meter readings in this column.
***For No. 2 diesel, use 7.05 Ib/gal (0.84 kg/L); for gasoline use 6.0 Ib/gal (0.72 kg/L); or actual specific weight of fuel
can be used.
1
(T2-T1) x tank capacity x 0.0005 + pump reading = corrected pump
2
Measure DEF gallons for all runs of the day as opposed to each individual run.
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —29
FORM 2-2: TYPE II—FUEL ECONOMY TEST DATA
BASELINE SEGMENT OF THE TEST VEHICLE
Type II Test—Portable Fuel Tank Weighing Method or Fuel Flow Meter Method
Fleet
Test Tractor #
Test Trailer #
Driver
Observer
Test #
Date
Test Speed
Route
Test Run #1
Scale Repeatability Check Weight
Fuel Weight/Fuel Meter Reading/Pump Corrected1
Odometer
Time
Start
Finish
Fuel Used
Ib/gal kg/L (circle one)
Time from Start to Finish
h
m
s
Subtract Vehicle Stopped Time
h
m
s
Vehicle Running Time*
h
m
s
Test Run #2
Scale Repeatability Check Weight
Fuel Weight/Fuel Meter Reading/Pump Corrected1
Odometer
Time
Start
Finish
Fuel Used
Ib/gal kg/L (circle one)
Time from Start to Finish
h
m
s
Subtract Vehicle Stopped Time
h
m
s
Vehicle Running Time*
h
m
s
Test Run #3
Scale Repeatability Check Weight
Fuel Weight/Fuel Meter Reading/Pump Corrected1
Odometer
Time
Start
Finish
Fuel Used
Ib/gal kg/L (circle one)
Time from Start to Finish
h
m
s
Subtract Vehicle Stopped Time
h
m
s
Vehicle Running Time*
h
m
s
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —30
FORM 2-2: TYPE II—FUEL ECONOMY TEST DATA (Continued)
Test Run #4
Scale Repeatability Check Weight
Fuel Weight/Fuel Meter Reading/Pump Corrected1
Odometer
Time
Start
Finish
Fuel Used
Ib/gal kg/L (circle one)
Time from Start to Finish
h
m
s
Subtract Vehicle Stopped Time
h
m
s
Vehicle Running Time*
h
m
s
Test Run #5
Scale Repeatability Check Weight
Fuel Weight/Fuel Meter Reading/Pump Corrected1
Odometer
Time
Start
Finish
Fuel Used
Ib/gal kg/L (circle one)
Time from Start to Finish
h
m
s
Subtract Vehicle Stopped Time
h
m
s
Vehicle Running Time*
h
m
s
Weather:
Temperature
Humidity
Barometric
Pressure
Wind Speed
Wind
Direction
Run #1
Run #2
Run #3
Run #4
Run #5
Total DEF Used for All Runs This Day _______________gal / L (circle one) (See Footnote 2)
* Running time must repeat within ±18 seconds for a one hour run or ± 0.5% of the time required to complete the test
run or the run data point must not be used. See paragraphs 3.2, 3.3, 5.5, & 5.9.
1
(T2-T1) x tank capacity x 0.0005 + pump reading = corrected pump
2
Measure DEF gallons for all runs of the day as opposed to each individual run.
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —31
FORM 2-3: TYPE II—FUEL ECONOMY TEST DATA
TEST SEGMENT OF THE CONTROL VEHICLE
Type II Test—Portable Fuel Tank Weighing Method or Fuel Flow Meter Method
Fleet
Control Tractor #
Control Trailer #
Driver
Observer
Test #
Date
Test Speed
Route
Test Run #1
Scale Repeatability Check Weight
Fuel Weight/Fuel Meter Reading/Pump Corrected1
Odometer
Time
Start
Finish
Fuel Used
Ib/gal kg/L (circle one)
Time from Start to Finish
h
m
s
Subtract Vehicle Stopped Time
h
m
s
Vehicle Running Time*
h
m
s
Test Run #2
Scale Repeatability Check Weight
Fuel Weight/Fuel Meter Reading/Pump Corrected1
Odometer
Time
Start
Finish
Fuel Used
Ib/gal kg/L (circle one)
Time from Start to Finish
h
m
s
Subtract Vehicle Stopped Time
h
m
s
Vehicle Running Time*
h
m
s
Test Run #3
Scale Repeatability Check Weight
Fuel Weight/Fuel Meter Reading/Pump Corrected1
Odometer
Time
Start
Finish
Fuel Used
Ib/gal kg/L (circle one)
Time from Start to Finish
h
m
s
Subtract Vehicle Stopped Time
h
m
s
Vehicle Running Time*
h
m
s
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —32
FORM 2-3: TYPE II—FUEL ECONOMY TEST DATA (Continued)
Test Run #4
Scale Repeatability Check Weight
Fuel Weight/Fuel Meter Reading/Pump Corrected1
Odometer
Time
Start
Finish
Fuel Used
Ib/gal kg/L (circle one)
Time from Start to Finish
h
m
s
Subtract Vehicle Stopped Time
h
m
s
Vehicle Running Time*
h
m
s
Test Run #5
Scale Repeatability Check Weight
Fuel Weight/Fuel Meter Reading/Pump Corrected1
Odometer
Time
Start
Finish
Fuel Used
Ib/gal kg/L (circle one)
Time from Start to Finish
h
m
s
Subtract Vehicle Stopped Time
h
m
s
Vehicle Running Time*
h
m
s
Control Vehicle MPG Calculation
Total Fuel Used
Total Fuel Used Ib/gal or
Total Miles (km) o f Run
Miles (km) of Run
kg/L**
Ib/gal
÷
÷
kg/L (circle one)
Time
÷***
=
gal (L) used =
h =
miles/h (km/h)
Weather:
Temperature
Humidity
h
m
gal (L)
miles/gal (km/L)
Barometric
Pressure
Wind Speed
s
Wind
Direction
Run #1
Run #2
Run #3
Run #4
Run #5
Total DEF Used for All Runs This Day _______________gal / L (circle one) (See Footnote 2)
* Running time must repeat within ±18 seconds for a one hour run or ± 0.5% of the time required to complete the test
run or the run data point must not be used. See paragraphs 3.2, 3.3, 5.5, and 5.9.
** If fuel meter is used, record meter readings in this column.
***For No. 2 diesel, use 7.05 Ib/gal (0.84 kg/L); for gasoline use 6.0 Ib/gal (0.72 kg/L); or actual specific weight of fuel
can be used.
1
(T2-T1) x tank capacity x 0.0005 + pump reading = corrected pump
2
Measure DEF gallons for all runs of the day as opposed to each individual run.
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —33
FORM 2-4: TYPE II—FUEL ECONOMY TEST DATA
TEST SEGMENT OF THE TEST VEHICLE
Type II Test—Portable Fuel Tank Weighing Method or Fuel Flow Meter Method
Fleet
Test Tractor #
Test Trailer #
Driver
Observer
Test #
Date
Test Speed
Route
Test Run #1
Scale Repeatability Check Weight
Fuel Weight/Fuel Meter Reading/Pump Corrected1
Odometer
Time
Start
Finish
Fuel Used
Ib/gal kg/L (circle one)
Time from Start to Finish
h
m
s
Subtract Vehicle Stopped Time
h
m
s
Vehicle Running Time*
h
m
s
Test Run #2
Scale Repeatability Check Weight
Fuel Weight/Fuel Meter Reading/Pump Corrected1
Odometer
Time
Start
Finish
Fuel Used
Ib/gal kg/L (circle one)
Time from Start to Finish
h
m
s
Subtract Vehicle Stopped Time
h
m
s
Vehicle Running Time*
h
m
s
Test Run #3
Scale Repeatability Check Weight
Fuel Weight/Fuel Meter Reading/Pump Corrected1
Odometer
Time
Start
Finish
Fuel Used
Ib/gal kg/L (circle one)
Time from Start to Finish
h
m
s
Subtract Vehicle Stopped Time
h
m
s
Vehicle Running Time*
h
m
s
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —34
FORM 2-4: TYPE II—FUEL ECONOMY TEST DATA (Continued)
Test Run #4
Scale Repeatability Check Weight
Fuel Weight/Fuel Meter Reading/Pump Corrected1
Odometer
Time
Start
Finish
Fuel Used
Ib/gal kg/L (circle one)
Time from Start to Finish
h
m
s
Subtract Vehicle Stopped Time
h
m
s
Vehicle Running Time*
h
m
s
Test Run #5
Scale Repeatability Check Weight
Fuel Weight/Fuel Meter Reading/Pump Corrected1
Odometer
Time
Start
Finish
Fuel Used
Ib/gal kg/L (circle one)
Time from Start to Finish
h
m
s
Subtract Vehicle Stopped Time
h
m
s
Vehicle Running Time*
h
m
s
Weather:
Temperature
Humidity
Barometric
Pressure
Wind Speed
Wind
Direction
Run #1
Run #2
Run #3
Run #4
Run #5
Total DEF Used for All Runs This Day _______________gal / L (circle one) (See Footnote 2)
* Running time must repeat within ±18 seconds for a one hour run or ± 0.5% of the time required to complete the test
run or run data point must not be used. See paragraphs 3.2, 3.3, 5.5, & 5.9.
1
(T2-T1) x tank capacity x 0.0005 + pump reading = corrected pump
2
Measure DEF gallons for all runs of the day as opposed to each individual run.
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —35
FORM 2-5: DEF Cost in $/mile for Results Calculation Worksheet
Date of Work ______________________________
Total miles run for all runs valid and not valid per fuel use, T over C are used for DEF use calculation.
Runs included in Calculation were run on:
Date (s)
Run #
From
To
___/___/____; 1___________(to)___________
___/___/____; 2___________(to)___________
___/___/____; 3___________(to)___________
___/___/____; 4___________(to)___________
___/___/____; 5___________(to)___________
Miles or km Run
___________
___________
___________
___________
___________
Total miles between DEF tank fills (sum above) ___________
DEF Cost to be used
___________ $/gal or $/liter
DEF used from measurement data sheet
___________ gal or liter
DEF cost in $/mile or liter/km =
(_______$/gal or $/km) X (______gal or liters Used) = ______$/mile or $/km DEF Cost
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —36
FORM 2-6: TYPE II — FUEL ECONOMY TEST
THE OBSERVER’S WORKSHEET
Fleet
Date
Observer’s Name
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —37
Test #
FORM 3-1: TYPE II—FUEL ECONOMY TEST DATA
CALCULATION SUMMARY SHEET
Fleet____________________________
Baseline Runs
1
Baseline
2
Data
3
4
5
Date _________________ Test # ______________
Test Vehicle
Fuel Used,
Ib/gal kg/L (circle one)
Form #2-2
Control Vehicle
Fuel Used,
Ib/gal kg/L (circle one)
T/C
Form #2-1
Ratio
Check Valid
T/C Ratios
Used
Note: Use only valid T/C ratios for calculation of average T/C.
Sum of valid baseline T/C ÷ No. of valid baseline T/Cs = average baseline T/C
÷
Baseline Runs
Test Vehicle
Fuel Used,
Ib/gal kg/L (circle one)
Form #2-2
1
Baseline
2
Data
3
4
5
=
Control Vehicle
Fuel Used,
Ib/gal kg/L (circle one)
T/C
Form #2-1
Ratio
Note: Use only valid T/C ratios for calculation of average T/C.
Sum of valid baseline T/C ÷ No. of valid baseline T/Cs = average baseline T/C
÷
=
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —38
Check Valid
T/C Ratios
Used
FORM 3-1: TYPE II—FUEL ECONOMY TEST DATA (Continued)
CALCULATION OF T/C LIMITS (FORM 3-1)
Fleet
Date
Test #
After 3 Runs:
Highest T/C Ratio
x 0.98
=
minimum acceptable T/C ratio
After 4 Runs:
Highest T/C Ratio
x 0.98 =
minimum acceptable T/C ratio
Second Highest T/C Ratio
x 0.98 =
minimum acceptable T/C ratio
Highest T/C Ratio
x 0.98
=
minimum acceptable T/C ratio
Second Highest T/C Ratio
x 0.98
=
minimum acceptable T/C ratio
Third Highest T/C Ratio
x 0.98
=
minimum acceptable T/C ratio
After 5 Runs:
FORM 3-2: TYPE II — CALCULATION OF % FUEL SAVED
Fleet
Date
Test #
% Fuel Saved = (Ave. Baseline T/C – Ave. Test T/C) ÷ Ave. Baseline T/C
% Fuel Saved = (
–
)
÷
% Fuel Saved =
Calculation of % Improvement:
% Improvement = (Ave. Baseline T/C – Ave. Test T/C) ÷ Ave. Test T/C
% Improvement = (
–
) ÷
% Improvement =
Note: See Appendix 1, Sample Calculations, to convert to mpg (km/L).
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —39
FORM 3-3: TYPE II—FUEL ECONOMY TEST DATA
Fleet
Date
Test #
Test Results:
% fuel saved after change
% improvement in fuel economy after change (describe below):
©2013—TMC/ATA
Proposed RP 1102A(T) Ballot Version —40
Recommended Practice
Proposed RP 1111B(T)
VMRS Various
RELATIONSHIPS BETWEEN TRUCK COMPONENTS
AND FUEL ECONOMY
PREFACE
The following Recommended Practice is subject to
the Disclaimer at the front of TMC’s Recommended
Maintenance Practices Manual. Users are urged to
read the Disclaimer before considering adoption of
any portion of this Recommended Practice.
consumption rates between 5.50-7.25 mpg for the
moving truck. Non-moving or idle fuel consumption
must be subtracted from these values. Additionally,
the effect of significant wind has not been factored
into these values. On windy days, the horsepower
demand would be higher.
SCOPE AND OBJECTIVE
This RP provides equipment operators with a basic awareness of the relationships between truck
components and fuel economy—along with an
understanding of how other variables also affect
fuel consumption. Because the number of possible
vehicle applications is enormous, the scope of this
RP is limited to Class 8 tractors coupled to 48-53
ft. single and double trailers with maximum gross
weights of 80,000 lbs.; in dry or refrigerated van
applications with maximum vehicle speeds of 65-70
mph. Though many of the principles apply to other
applications, the percentages shown are given only
for this specific application range.
DATA VALIDITY
The fuel economy improvements discussed in this RP
will vary significantly with component combinations
between both fleets and individual vehicles. Though
it would be possible to reduce the data variance for
many of these components through additional testing,
the cost would be prohibitive, and the results would
be “brand specific.” The information presented in
this RP is sufficient to provide general guidance on
the relationships between component specification
and fuel economy.
NOTE: Component or engine control strategies are
not additive when combining two or more options.
POWER DEMAND AND FUEL CONSUMPTION
The data shown in Chart 1 is valid as long as vehicle
power demands are between 160-220 hp. As Chart
1 shows, these power demands will result in fuel
CHART 1
EFFECT OF POWER DEMAND
ON FUEL ECONOMY
©2013—TMC/ATA
USE OF THIS DATA
Equipment users should view this document: (a) as a
source of general ideas to improve fuel consumption,
or (b) to explain why fuel consumption expectations
are not being met. Equipment users must conduct
their own specific tests before making purchasing
decisions.
CRUISE CONTROL
Cruise control settings and logic can significantly
affect fuel economy. Things such as “softcruise”
combined with vehicle speed limits and droop curves
do need to be set properly to maximize the positive
effects of cruise.
Though the best drivers are able to consistently obtain
better fuel consumption with “their foot,” average drivers typically get better mpg when using cruise control.
Cruise control corrects major errors made by average
drivers relating to changes in engine power output.
For example, a tendency to accelerate unnecessarily
when going up “small hills,” is a typical overcorrection made by average drivers. With experience,
drivers learn that the true slope of a grade may be
higher than what they think they see. This prompts
them to raise power levels when they sense or see
Proposed RP 1111B(T) Ballot Version—
Issued 4/1997
Revised x/xxxx
COOLING FANS
Historically, viscous fan drives have increased fuel
consumption because they never turn completely off.
Newer viscous fan designs may reduce horsepower
demand and mpg loss associated with viscous drives
to the lowest level as shown in Table 2. Newer viscous
fan drives have been introduced that operate as on-off,
variable speed and multi-speed. Depending on duty
cycle the result is lower average horsepower demand
by the fan and improved fuel consumption.
a hill; resulting in more power use than is needed to
maintain speed while climbing small hills.
GEARING
Engine manufacturers recommend specific cruise
RPMs for different engines. Generally, the recommended RPM is lowered when engine displacement
increases. Fuel consumption increases when gearing that needs higher RPM to attain cruise speeds
is used. A 70 RPM difference at cruise speed is a
typical result of changing axle ratios by one available
ratio—that is changing from 3.70 rear ends to 3.90
rear ends. (See Table 1.)
Unwanted fan activity can be very detrimental to
fuel consumption. Current cooling fans can have
horsepower demand as high 70 hp. Although it is
rare— but possible—for a truck to be operated for
months with the fan “locked on,” there are some
trucks with 10 to 30 percent unneeded fan activity.
This normally comes from mismatching components.
An example is the use of 200oF thermostats in an
engine which has the fan control system programmed
for 180oF thermostats. Another significant source of
unwanted fan activity is an improperly maintained air
conditioning system or air conditioning-to-fan clutch
control system.
One hundred percent fan ON time can result from
failures of fan clutches or their control systems. Higher
amounts of fan ON time can result from high- density
radiator, charge air, or air conditioning condenser
cores that do not provide sufficient cooling on small
grades or in very high ambient temperatures with
ram air flow alone. (High-density refers to increased
number of fins per inch of core or other designs which
restrict the air flow through the cooling system.)
Therefore, these high-density cores need more fan
ON time than low-density designs that have less
resistance to air flow. Failure to keep the airside
of cooling system cores free of debris, trash, dirt,
leaves, bugs, etc., may sufficiently restrict air flow,
resulting in significant increases in fan ON time. In
many trucks with air conditioning, the fan can be
turned on by the air conditioning system. In trucks
so equipped, poor maintenance or air conditioning
system failures can result in high amounts of fan ON
time. A fan that does not “totally” disengage (as with
viscous fan drives), consumes some power and fuel
at the minimum speed the fan drive can attain.
Some trucks are equipped with driver-operated
switches for fan control. These trucks leave fan ON
time to the driver’s discretion. Abuse by an unknowing
driver will result in unrequired parasitic fan horsepower
loads and consequently a loss in mpg.
©2013—TMC/ATA
Proposed RP 1111B(T) Ballot Version—
WINTER FRONTS
Winter fronts can assist with enhanced aerodynamic
characteristics, although the driver that does not remove the winter front in temperatures above freezing
can initiate unneeded fan on time. A properly designed
winter front will not close off more than 75 percent
grill opening and be designed with full core length
stripped openings running perpendicular to the air
flow tubes in the charge air cooler.
INTAKE AND EXHAUST RESTRICTION
Engine fuel consumption is adversely affected as
the effort required to get air into and exhaust gas out
of the engine is increased. Though not a parasitic
horsepower loss—as are cooling fans—the net effect of increasing intake restriction and exhaust back
pressure on fuel consumption is similar to adding
parasitic losses.
TABLE 3: INTAKE & EXHAUST RESTRICTION
If you use/have:
vs.
MPG
Improves
No Intake
Restriction
25" of Water
Up to 1%
No exhaust
Restriction
40" of Water
0.3-2%
Intake restriction is a function of both intake system
design and maintenance. In considering maintenance
changes to improve fuel consumption, care must be
exercised in the pay-back calculations, as the losses
are typically small. Exhaust back pressure is set by
system design; i.e., there is little or no maintenance
of mufflers. Though changes resulting from exhaust
restriction are small, paying attention to exhaust
back pressure during truck spec’ing can yield some
savings. (See Table 3.)
2007 DIESEL PARTICULATE FILTER EXHAUST
BACK PRESSURE RESTRICTIONS
Heavy-duty engine designs for the 2007 model year
require the use of a diesel particulate filter (DPF)
that increases back pressure in the range of 3-8.5"
Hg. These engines are designed to operate within
these parameters and will alert the driver when the
filter needs to be serviced.
AIR COMPRESSORS
Fuel consumption losses can be primarily caused
by the higher horsepower demands associated with
larger displacement compressors when the compressors are not pumping. (See Table 4.)
©2013—TMC/ATA
IDLING
TMC RP 1108, Analysis of Costs from Idling and
Parasitic Devices for Heavy-duty Trucks, covers
the subject of idling in much more detail. The values, shown in Table 5, are “ball park” values that
equipment users can use as a reference. Though
some readers may be surprised by the inclusion of
values for 50 percent idle time, 50 percent idle time
is unfortunately common in single operation sleeper
tractors. The increased loss at 1,000 RPM caused
by air conditioning is due to higher fuel rates associated with both running the air conditioning system
and engine at a higher idle speed. Note also that
most engine manufacturers recommend maximum
idle speeds at 900 rpm to diminish soot loading of
the 2007 aftertreatment systems, thereby requiring
less regeneration activity ( less fuel used to drive
active regeneration).
TABLE 5: IDLING
If you
use/have:
vs.
MPG
Improves
With A/C ON @ 1000 RPM
Zero Idle Time
50%
7-10%
Zero Idle Time
25%
3-6%
Zero Idle Time
10%
2-3%
With Engine Only @ 700 RPM
Zero Idle Time
50%
3-4%
Zero Idle Time
25%
1-2%
Zero Idle Time
10%
0.5-1%
See TMC RP 1109 for more information.
AERODYNAMICS
Truck-trailer aerodynamics is a complicated subject.
This RP only scratches the surface of aerodynamic
issues. In many cases, values (such as shown in
Figure 1) expressed are stated as “up to.” The reason
for this is that similar aerodynamic devices may not
deliver the same performance. Some devices may
look good but not perform as well as they look; and
Proposed RP 1111B(T) Ballot Version—
Figure 1
some devices may offer no improvement because
of the way they are designed or applied. TMC’s RP
1109, Type IV Fuel Economy Test Procedure, is an
excellent tool for equipment users to evaluate aerodynamic devices.
The values for trailer gap, shown in Table 6, can be
either from the back of the cab [for tractors without
cab extenders] or from the back of the cab extenders.
Cab extenders are an effective way to reduce the
trailer gap. The values shown for standard deflector
and full-roof fairings coincide with industry results.
A standard deflector is a roof-mounted device that
does not have the sides closed and does not extend
back of the cab. A full-roof fairing has the sides closed
above the roof of the cab and often extends back of
the cab. A raised roof sleeper has a high roof to allow
the driver to stand up. The comparison is made to a
full-roof fairing. The four- to six-percent loss, shown
in Table 6, results from air at the top of the raised
roof sleeper being directed into the front of the trailer
rather than over the top as should happen with the
full-roof fairing.
Air dam front bumpers reduce aerodynamic drag by
preventing air from getting to the aerodynamically
“dirty” underside of the tractor. (The high aerodynamic drag of axles, oil pans and other components
with poor aerodynamic shapes makes this location
aerodynamically “dirty.”) Tractor side skirts also are
able to keep the air flow away from the aerodynamically “dirty” components found under the tractor, and
they aid in getting air flow attached to the sides of
the tractor near the ground. Without side skirts, air
flow along the sides of a tractor near the ground is
very turbulent. Turbulence is the prime contributor
to high aerodynamic drag.
Trailer side skirts have been documented to improve
fuel efficiency up to six percent. The fuel savings is
©2013—TMC/ATA
presently being weighed against the added weight
and maintenance costs associated with the add-on
devices.
Bug deflectors are popular with drivers because they
keep bugs off the windshield. Unfortunately, they
do that by creating turbulence which creates more
drag. There is an argument that a bug deflector can
be designed that would not hurt fuel consumption.
The Task Force accepts this is possible. However,
no data indicates “better fuel consumption” bug
deflectors are available.
The “Dead Bug” Rule
The presence of dead bugs anywhere on the front of
the tractor or trailer clearly indicates an aerodynamic
problem. However, the absence of dead bugs does
not necessarily indicate good aerodynamics.
Proposed RP 1111B(T) Ballot Version—
Other Aerodynamic Issues
Though no specific values are presented, the addition
of certain components into the air stream can cause
added drag that’s detrimental to fuel consumption.
Typical examples of these components include external air cleaners, exhaust stacks, and extra mirrors.
Though no data is presented, installation of exhaust
stacks behind a full roof fairing or underneath the
tractor is more aerodynamic and will improve mpg.
To feel the effect of these components being put in
the air stream, observe the force on your arm when
it is placed out the window of a truck or car with your
palm forward running at 65 mph for a few seconds.
Note that wind tunnel research has documented
gaps too close will actually decrease the aerodynamic efficiency of a tractor-trailer combination. Seek
manufacturer recommendations.
The reduction in fuel economy from components
placed into the air stream can be estimated by:
% MPG =
(Component Forward projected Area in ft2) x (0.3)
Example:
A bug deflector of 3 ft2 decreases fuel economy 0.9
percent.
SPEED
Average vehicle speed has a large effect on fuel
consumption. Again, it is important to remember
that the values in this RP are for Class 8 tractors,
grossing 80,000 lbs., with 8.5 ft. by 13.5 ft. vans
or refrigerated trailers running 65-70 mph. If lower
gross weights were used, the percentages for fuel
consumption loss with increased speed would be
higher. This occurs because the change in aerodynamic horsepower demand is greater with speed
than the increase due to rolling resistance. Trucks
with poor aerodynamics suffer much larger losses
TABLE 7: SPEED
If you go slower:*
MPG Improves
With Excellent Aerodynamics
1 mph
1-1.5%
5 mph
5-8%
With Poor Aerodynamics
1 mph
2-3%
5 mph
10-15%
* Between 65-70 mph. All based on changes in average speed—typically average
speed changes are less than maximum speed changes
©2013—TMC/ATA
in mpg as speed increases than do trucks with good
aerodynamic characteristics for the same reasons.
That is, since the increase in horsepower demand
with speed is a cubic function, the truck with high
aerodynamic drag has a much higher horsepower
demand increase than does the truck with low drag
and good aerodynamics. (See Table 7.)
In Table 7, excellent aerodynamics represent a
tractor-trailer with full fairings that yield a 0.58 drag
coefficient. An example, of a poor aerodynamics
treatment is an untreated tractor pulling a dry-van or
refrigerated trailer with a 0.80 drag coefficient. The
effect of poor aerodynamics in this example will essentially double the fuel loss consumption associated
with increasing vehicle speed.
Table 7 shows average speed changes of the vehicle.
Although there is an increase in average speed when
maximum vehicle speed is increased, the relationship
is not linear. That is, when maximum vehicle speed
is increased by five mph, it is not likely that average
speed will increase by more than three mph.
Equipment users need to measure the average
speed change that results from maximum speed
changes. The results will vary as a function of engine
horsepower, vehicle horsepower demand, routes,
speed limits (enforced rather than posted) and most
importantly what the maximum speed was before the
increase. If the enforced speed limit is 65 mph when
the maximum speed of a truck is changed from 60 - 65
mph, the average speed increase will be much closer
to five mph than if the maximum speed is changed
from 70 to 75 mph with a 75 mph enforced speed
limit. With electronic engines, fleets can measure
average speed changes. Average speed, or the data
in miles and hours to calculate average speed, can
be down- loaded from the engine electronic control
module.
The effect of controlling speed in reducing fuel consumption is very significant. Cost savings can also be
realized from other truck components with reduced
speed. Equipment users must weigh these reduced
operation costs and other benefits against productivity
or utilization gains obtained from increased speed.
TMC’s 55 vs 65+ Technical Report is an excellent
reference for making such productivity decisions. To
order, call (703) 838-1763.
Note that trucks that are properly geared for 70 mph
may not perform up to expectations from a driver's
viewpoint when maximum road speed is reduced to
Proposed RP 1111B(T) Ballot Version—
65 mph (approximately 110 RPM). When using this
technique it is important that the performance of the
vehicle be explained to drivers. And it is important
to understand the performance of the vehicle at
peak torque RPM and or the downshift point. The
goal of applying the “gear fast-run slow” technique
to transmission selection is establishing a downshift
point acceptable to drivers that does not significantly
reduce vehicle performance.
EXCESSIVE USE OF BRAKES
Though largely a driver training issue, the excessive
use of brakes affects fuel consumption. The brakes,
either engine brakes of service brakes, remove energy
from the vehicle. Thus, more-than-essential use of the
braking system for safe truck operation will increase
fuel usage. Some electronic engines have features
that automatically apply engine brakes when the
desired vehicle speed is exceeded; though this may
be good for other reasons, there is often a loss in fuel
economy when a feature that automatically applies
the engine brake is activated on electronic engines.
TMC has no data giving the amount of fuel mileage
loss associated with excessive brake use.
CRUISE ENGINE BRAKES
Electronic parameters should be set to allow taking advantage of downhill runoff due to gravity and
inertia before the next upgrade. A three mph setting
for initial retardation can be beneficial. Initial testing
has indicated that improperly programmed engine
TABLE 8: TIRES
MPG
Improves
cruise brakes can affect fuel consumption by up to
two percent when set too close to cruise speeds,
terrain dependent.
TIRES
Equipment users should contact their tire manufacturers for detailed information on rolling resistance and
its effect on fuel economy. Though tire construction
variables can be significantly different—both within a
tire manufacturers product line and between manufacturers—typically tire tread depth is an predictor of
fuel economy performance. (See Table 8.)
Tire makers indicate a six percent increase in efficiency at half worn tread depth and a 6.6 percent
increase at 80 percent worn tread depth. Incorrectly
programmed tire sizes calculate distance incorrectly
thereby miscalculating overall mpg.
More tread will generally increase the rolling resistance and hurt fuel economy. The rubber compound used can obviously have an impact on both
original and retreaded tires. Initial tire construction
significantly influences retread tire fuel economy.
However, retread processing (such as the amount
of original undertread left on the casing before retreading) also has a significant effect on retread tire
fuel consumption.
Tire Balance
Tire balance across 18 tires on a tractor-trailer combination has been documented to save as much as
2.2 percent in SAE J1326/RP 1102 Type II testing
at two different facilities.
If you use:
vs.
S/D/T
S/D/T
Rib/Rib/Rib
Rib/Lug/Rib
2-4%
Rib/Lug/Rib
Rib/Deep
Lug/Rib
2-5%
Rib/Lug
Shallow Rib
Rib/Lug/
Std. Rib
2-5%
Rib/Rib/
Shallow Rib
Rib/Lug/
Std. Rib
4-9%
Rib/Rib/
Shallow Rib
Rib/Deep
Lug/Rib
6-14%
If you use/have:
vs.
Rib/OT/OT
Rib/Retread/
Retread
MPG
Improves
Up to 7%
No Headwind
5 mph
Headwind
5-10%
No Crosswind
5 mph
Crosswind
Up to 10%
S=Steer D=Drive T=Trailer
OT=Original Tread
©2013—TMC/ATA
WIND
Though wind could have been presented in this RP
under “Aerodynamics,” it is included under a separate
heading because TMC has no data showing how
aerodynamics and wind speed direction are related.
However, TMC agrees that vehicles with good aerodynamic characteristics will not have fuel economy
losses in windy conditions that are as great as those
with poor aerodynamics.
TABLE 9: WIND
Proposed RP 1111B(T) Ballot Version—
TABLE 10: TRANSMISSIONS
If you use/have:
vs.
MPG
Improves
Direct Drive
Overdrive*
Up to 3%
* With same engine cruise RPM
The effect of direct head and tail winds is not difficult
to understand. However, the effects of cross winds
are much more difficult to both understand and
predict. Wind direction that has the worst effect on
fuel consumption is a quartering wind into the front
of the tractor.
Further, the ability to show improved fuel economy
with a good aerodynamic package is enhanced by
front, quartering winds. Note also that average wind
speed increases in the winter and spring months
compared to summer and fall months.
TRANSMISSIONS
This RP does not address all the issues associated
with transmission gearing because there is so much
variation in what is needed for optimal fuel economy
that is a function of engine design, routes, driver
preferences and truck performance issues.
There are a number of computer simulation programs
available in the industry. Simulation software assists
equipment users in making correct transmission
gearing selections for the engine, routes and loads
involved.
It is important when using these simulations to recall
that comparisons of simulations from different vendors
is normally subject to error because the calculations between two programs may be significantly
different. It is also important to remember that all
these programs are subject to “garbage in garbage
out” errors. Therefore, when using these programs,
take care to ensure that runs being compared have
the correct data. Make sure all variables are held
constant and that correct differences are entered
for true comparison.
One frequently asked question is: “What is the
difference between direct and overdrive transmissions?”
TMC has learned that at least a two percent improvement in fuel economy can be expected by using
direct drive transmissions if operated in top gear at
least 80 percent of the time. Greater efficiencies
©2013—TMC/ATA
TABLE 11: TRANSMISSION/AXLE LUBE
If you use/have:
vs.
Synthetic
Mineral Oil
MPG
Improves
Summer
Up to 0.5%
Winter
Up to 2%
have been documented. Equipment users should
contact driveline suppliers to ensure the driveline is
adequately engineered.
NOTE: Proper geared engine speed may be compromised with a direct drive transmission due to
limitations on axle ratios, depending on the present
overdrive ratio and axle combination.
Other information indicates that higher differences
in favor of the direct in high gear transmission could
be realized for trucks. (See Table 10.)
AXLE AND TRANSMISSION LUBE
Synthetic lubricants offer small reductions in shear
forces associated with the lube oil at all temperatures.
The largest effect is at low ambient temperatures.
Synthetic lubricants outperform mineral oil lubricants
with respect to fuel economy, particularly in winter
conditions. (See Table 11.)
TANDEM DRIVE VERSUS SINGLE DRIVE
WITH TAG (OR PUSHER) TRACTOR AXLES
The improvement with tag axles results from eliminating the parasitic horsepower loss associated with
not having a second axle ring and pinion and from
similarly not having the losses associated with the
interaxle differential (i.e. the power divider). Though
there is a clear fuel saving, fleets should evaluate
potential operational problems including loss of
traction in adverse conditions and possible loss of
resale value before adopting this drive arrangement.
(See Table 12.)
TABLE 12: TANDEMS vs. TAGS
If you use/have:
vs.
MPG
Improves
Single Drive
With Tag
Tandem Drive
2-3%
Proposed RP 1111B(T) Ballot Version—
TABLE 13: COLD WEATHER
TABLE 15: ROUTES, WEIGHT & DRIVERS
vs.
MPG
Improves
10°F Warmer Air
Temperature (Up
to 77°F)
No Change
2% per 10°F
Without Fan
On Time
Influence
Summer
Winter
8-12%
Summer Fuel
Winter Fuel
Up to 3%
If you use/have:
COLD WEATHER
The effect of cold weather on fuel consumption results
from colder lubricants and the additional aerodynamic
load of denser air. Average wind speed is higher in
most of North America during winter. The use of lubricants with better low temperature characteristics
may improve cold weather fuel consumption: but,
equipment users should evaluate possible savings in
their operations before deciding to use them. Trucks
with very good aerodynamics will have smaller losses
associated with colder, denser air and higher average
wind speeds. (See Table 13.) The 8-12 percent shown
for summer vs. winter in Table 13 was reported by
fleets as typical. Summer vs. winter fuel difference is
the result of the lower energy content associated with
the lighter fuels typically found in cold climates.
“BREAK-IN” PERIODS
During the first few thousand miles of service, new
vehicles typically experience a reduction in parasitic
losses associated with rolling and sliding surfaces
“wearing in.” In some cases there is a reduction in
disengaged brake drag. Fuel consumption comparisons between trucks, tractors, and trailers should not
be made until they have accumulated 10,000 miles
of operation. (See Table 14.)
ROUTES, WEIGHT, AND DRIVERS
Routes, weight, and drivers have significant effects
on fuel consumption. These are very important considerations when fuel consumption results for units
in a fleet or total fleets are being compared. The
information presented on routes shows how having
TABLE 14: BREAK-IN PERIOD
If you use/have:
vs.
MPG
Improves
Truck with
10,000 Miles
(Tires Not
Included)
Zero Mile
Truck
2-5%
©2013—TMC/ATA
If you use/have:
vs.
MPG
Improves
Flat Interstate
Highway
Flat 2-Lane
Highway
4-11%
Flat Interstate
Highway
Mountainous
Interstate
4-18%
Flat Interstate
Highway
Suburban
Route with
Stop and Go
25-35%
Flat Interstate
Highway
Urban Route
With 100%
Stop and Go
45-165%
WEIGHTS
And decrease weight 10,000 lbs. (for GVW
between 60,000-80,000 lbs.
Flat Route
6-10%
Mountain Route
7-12%
DRIVERS
Best Drivers
Worst Drivers
Up to 35%
to stop an 80,000 lb. vehicle often dramatically affects
fuel consumption. (See Table 15.)
Although there are a number of factors as to why
stopping the vehicle hurts fuel consumption, the
most significant is normally energy removed from the
vehicle by applying the service or auxiliary brakes.
Minimizing the use of braking systems and maximizing the coasting time saves fuel.
After stopping, fuel is also consumed at higher rates
during the ensuing vehicle acceleration. Flat interstate
highways offer the best fuel consumption potential
because they minimize unwanted speed changes
for traffic, towns, curves in the road, and downshifts.
Mountainous interstate routes take more fuel for
similar reasons. In a perfect situation, conservation of
momentum could make flat and mountainous routes
have the same fuel consumption. Mountainous routes
often require removing energy from the vehicle with
braking systems to maintain safe driving conditions.
Mountain routes also often require fuel consuming
accelerations from reduced speeds. Added weight
increases rolling resistance which increases fuel
consumption.
TMC believes that a 35 percent variance between
drivers in fuel economy performance is realistic.
Proposed RP 1111B(T) Ballot Version—
TABLE 16: TRAILERS
MPG
Improves
If you use/have:
vs.
Single Van
Double Van
Smooth Sides
Exterior Posts
2-4%
Trailer Side
Skirts
None
Up to 3%
Swing Doors
Up to 1.5%
Standard
Up to 0.5%
None
Up to 1%
Roll-up Doors
Aerodynamic
Mud Flaps
Wheel Covers
6-10%
As with routes, drivers can affect fuel consumption
by changing horsepower demand. The major driver
effects are: idle time, vehicle speed, and brake use.
However, there are other driver factors that can affect
some operations. In suburban or urban operations,
truck acceleration rates and shifting techniques (that
is, use of progressive shifting) can be very important
variables. On trucks with sliding fifth wheels, the driver
can affect the trailer gap and thus the aerodynamics.
On trucks with switches for the fan clutch or winter
fronts, the driver can affect fan ON time. There are
other driver-effected variables; however, when considering the effects of drivers on fuel consumption,
vehicle speed, idle time, and brake use are the most
important. It is also critical to know how important
driver attitude is in fuel consumption. Anything that
makes the driver “mad” at the truck; steering wheel
“pulling,” high noise, bad seats, poor temperature
control, vibration, etc., hurts fuel consumption significantly.
TRAILERS
Table 16 shows the expected results for single vs.
double trailers, smooth vs. exterior posts vs. smooth
sides, and other trailer-related options.
MPG CALCULATIONS
When numbers from different trucks or fleets are
judged, an understanding of how compared mpg
©2013—TMC/ATA
values were derived is critical to making sound decisions. There are many variables in fuel consumption
and there are many ways to calculate mpg. See TMC
RP 354, Fuel Economy Tracking Guidelines.
The initial fill of the fuel tank can invalidate the
comparison of records between trucks in a fleet or
between fleets. If a truck has 200 gallon tanks and
190 gallons was added to the truck when it was put
in fleet service, and if the 190 gallon initial fill is used
in the fuel consumption calculations for a truck that
really gets 6.5 mpg; the calculated results will be 5.78
mpg at 10,000 miles, 6.34 mpg at 50,000 miles and
6.42 mpg at 100,000 miles.
There are many things that can affect mpg calculations including:
• speedometer calibrations.
• pulses per mile entry on electronic engines.
• both of the above items can be caused by
the wrong tire revolutions per mile. That is, by
using the information for the wrong tire size.
• map miles versus odometer miles.
• driver out-of-route miles when map miles used.
• missed trips when map miles are used.
Things that can affect fuel consumption are:
• fuel dispenser accuracy.
• calibration of electronic engine fuel totaling.
• two different electronic engine electronics.
• missing fuel addition records.
• fuel additions being credited to wrong truck.
• loss or theft of fuel from truck’s tanks.
• some or all reefer fuel charged to tractor, reefer
or auxiliary power unit (APU).
• some tractor fuel being charged to reefer.
SUMMARY
Use of this RP should help equipment users find ways
to reduce fuel costs. Remember, these are intended
only as guidelines. Individual fleet testing for more
specific data is recommended. The effects of all the
items in this RP are not necessarily additive if several
of them are applied at the same time.
Proposed RP 1111B(T) Ballot Version—
Recommended Practice
Proposed RP 1429 (T)
VMRS 053-999-007
UNDERSTANDING AUTOMATIC
TRANSMISSION DIVERSITY
PREFACE
The following Recommended Practice is subject to
the Disclaimer at the front of TMC’s Recommended
Maintenance Practices Manual. Users are urged to
read the Disclaimer before considering adoption of
any portion of this Recommended Practice.
informed decisions when selecting ATF and describe
factors that has led to the industry’s current ATF
diversity.
This RP also describes:
• the science behind ATF formulation.
• the evolution of hardware that necessitated
the development of new ATF specifications.
• concerns that may arise should an incorrect
fluid be introduced into the transmission.
• available ATF choices/options.
PURPOSE AND SCOPE
This Recommended Practice (RP) describes differences among automatic transmission fluids (ATFs)
currently used in Class 2-6 light- and medium-duty
vehicles. It is designed to help fleet managers make
Allison
TES-389
TES-295
Chrysler
ATF+2
ATF+4®
ATF+3
ATF+4® is a registered trademark of Chrysler.
Ford
MERCON®
Type A/B
MERCON®-V
MERCON® Rev
Type F/G
MERCON® Rev
MERCON®-V Rev
MERCON®-SP
MERCON® is a registered trademark of Ford.
General Motors
Type A
TASA
1950
1960
DEXRON®-IIE
DEXRON®-IIIH
DEXRON®-IV
DEXRON®-IID
1970
DEXRON®-IIIG
DEXRON®-IIIF
DEXRON®
DEXRON® is a registered trademark of GM.
MERCON®-C
MERCON®-LV
(never released)
1980
1990
2000
DEXRON®-VI
2010
Figure 1
© 2013—TMC/ATA
Proposed RP 1429 (T) Ballot Version—
Issued x/xxxx
BACKGROUND
Since 1950, manufacturers have developed 25 variants of ATF specifications. Of these, 24 have been
released to market. See Figure 1.
The resulting changes in specifications are driven
by many factors. ATF is one of the more complex
fluids used in automotive applications. It is comprised
of base oil, anti-wear agents, antioxidants, corrosion inhibitors, dispersants, foam inhibitors, friction
modifiers, pour-point depressants, seal swell agents,
viscosity index improvers, and red dye. How well
these components work together is measured by a
long-established process that tests, evaluates and
licenses ATF. Unlike engine oils, automatic transmission fluids are licensed by original equipment
manufacturers (OEMs).
ATFs are tasked to perform many critical functions.
Not only do these fluids serve as a torque-transfer
medium, they are instrumental in managing heat,
providing control and lubrication, maintaining proper
viscosity over a wide operating temperature range,
protecting against rust and corrosion, and controlling
shift quality, sludge, varnish and leaks.
DEVELOPMENT CHALLENGES
There are a number of development challenges to
manufacturing ATF including hardware considerations, transmission architecture, torque converter
design (e.g., continuous slip vs. lock-up clutch), step
ratios, transmissions (number of forward speeds),
etc. Add to this new innovations such as the con-
tinuously variable transmission (CVT), dual clutch
transmission.
Transmission design has certainly grown more
complex. More than 300 unique materials have been
used in the production of automatic transmissions.
Class 2-6 truck automatics have to serve a variety
of vehicle applications with gross vehicle weight ratings up to 26,000 lbs., and gross combined weight
ratings up to 32,000 lbs. New concerns over fuel
economy have also led to a need for lower viscosity
fluids, which reduce drag losses and thereby yield
incremental fuel economy improvements.
Equipment users also demand the same or increased
reliability and durability from automatics, despite
increasing performance demands and complexity.
Faced with all these competing demands, it typically
takes up to three years of component, transmission
and vehicle level testing (including fleets) to validate
a new ATF formulation.
See Table 1 for a typical ATF formulation.
Base Oil Group Definitions
There are three base oil groups in common use:
Group II, III and IV:
• Group II—Group II base oils are common
in mineral-based oils currently available.
They have good performance in lubricating
properties such as volatility, oxidative stability and flash/fire points. They have only fair
performance in areas such as pour point, cold
TABLE 1:
TYPICAL ATF FORMULATION
Component
Base oil
% Volume
76 – 90
Trend
Group II & III base oils
Better low temp properties
Additive package
• Friction modifiers
• Oxidation inhibitors
• Detergents/dispersants
• Corrosion inhibitors
• Anti-wear
• Seal swell agents
• Anti-foam
8 - 12
Friction durability/shudder resistance
Sludge resistance
Oxidation resistance/friction
Shudder resistance
Decreased gear wear
Better seal compatibility
Viscosity modifier
2 – 12
Very shear stable
Red dye
250 PPM
Red dye
© 2013—TMC/ATA
Proposed RP 1429 (T) Ballot Version—
crank viscosity and extreme pressure wear. Group II base stocks contain greater than or
equal to 90 percent saturates and less than or
equal to 0.03 percent sulfur and have viscosity index greater than or equal to 80 and less
than 120.
• Group III—Group III base oils are subjected to
the highest level of mineral oil refining of the
base oil groups. Although they are not chemically engineered, they offer good performance
in a wide range of attributes as well as good
molecular uniformity and stability. They are
commonly mixed with additives and marketed
as synthetic or semi-synthetic products. Group
III base oils have become more common in
America in the last decade. Group III base
stocks contain greater than or equal to 90
percent saturates and less than or equal to
0.03 percent sulfur and have viscosity index
greater than or equal to 120.
• Group IV—Group IV base oils are polyalphaolefin (PAO) base oils are manufactured from
olefins, a specific type of chemical feedstock.
When combined with additives, they offer
excellent performance over a wide range of
lubricating properties. These base oils are
referred to as traditional synthetics.
For additional information on base oils and additives
refer to TMC RP 624A, Lubricant Fundamentals.
ATF LABELING/MARKETING CATEGORIES
There are three categories of ATF in common use:
conventional, synthetic blend/semi-synthetic, and
full synthetic.
• Conventional—This is a lubricating oil that
is a byproduct of the crude that is extracted
from the ground which is then processed for
refining into a base oil.
• Synthetic Blend/Semi Synthetic—This is a
blend of conventional mineral oil with a specific
amount of fully synthetic base oil. There are
no standards or regulations within the industry
that explain how much “synthetic” a blend must
contain. So, it’s up to the manufacturer’s best
judgment as to what the definition of semisynthetic is.
• Full Synthetic—This is a lubricating fluid made
by chemically reacting materials of a specific
chemical composition to produce a compound
with planned and predictable properties.
Genuine OEM Fluids
Genuine OEM fluids are approved / licensed products
© 2013—TMC/ATA
that are tested by the OEM (or their approved labs),
and are OEM verified, licensed and recommended.
Different OEMs have unique fluid programs.
• Allison Transmission - TES
• Chrysler Corporation - ATF+4®
• Ford Motor Company - MERCON®
• General Motors Corporation - DEXRON®
The advantages of genuine OEM fluids are:
• specific design for the transmission
• OEM licensing
• peace of mind
• longer equipment life
• warranty coverage
• Incremental fuel economy improvements
• potentially lower operating costs
The disadvantages are:
• high cost (price and inventory)
• limited availability
• Inventory fragmentation
- too many fluids
- possible misapplication
- technician confusion
Premium Multi-Vehicle Fluids
Premium multi-vehicle fluids have been developed
to cover a wide range of OEM specifications. These
fluids can be used successfully in supported applications. While not necessarily a “one-size-fits-all”
solution, they may be suitable for use in a range of
OEM recommendations.
The advantages are:
• one fluid for many transmissions
• comparable quality to OEM fluids
• reduced fragmentation
• less confusion
• fewer misapplications
• potentially lower cost
The disadvantages are:
• uncertain suitability for a given application
(how do you know it will work?)
• no industry ATF standardization for multi-vehicle fluids
• may not be approved for a specific application
• warranty coverage may be compromised
Previously Approved Fluids
Previously approved (DEXRON®-III/MERCON®)
fluids are evaluated against older specifications.
While they may work in older Ford and GM vehicles,
there could be risk involved as they may not meet the
Proposed RP 1429 (T) Ballot Version—
intended specification. Their advantages are:
• low cost
• ready availability in the marketplace
• works in older GM and Ford vehicles
• multi-application fluid (hydraulic and manual
transmission fluid)
• evaluated vs. older specification (test data
available to support older specification)
Their disadvantages are:
• obsolete specification(s)
• no OEM approval system for fluids meeting
obsolete specifications.
• fluids may not actually meet the intended specification and are not forward compatible.
Fig. 2: Thermal Distress Leads to Glazing
and Clutch Slippage at 60,283 Miles
Generic Fluids
These fluids are usually no more than base oil with
red dye. The attraction to this fluid is generally low
cost. The fluids ability to perform is usually questionable at best.
Their advantages are:
• lower cost
Their disadvantages are:
• misapplication issues
• improper shifting
• slow or sluggish shifting
• shortened fluid life due to poor oxidation performance
• bushing wear
• gear wear
• friction material wear
• shortened transmission life
• warranty implications.
CONSEQUENCES OF FLUID MISAPPLICATION
The consequences of using an ATF not designed for
the transmission are:
• improper shifting
- mismatch of fluid and friction material
- clutch slipping or material damage
- burned or glazed clutches
- vibrations leading to shudder
- stuck valves
• slow or sluggish shifting
- fluid is too thick at low temperatures
- sludge/deposit formation due to oxidation
• bushing wear
- copper/bronze corrosion
• gear wear
© 2013—TMC/ATA
Fig. 3: Sludge and Debris From
Excessive Oxidation and
Contamination at 44,800 Miles
• seal damage (over swelling / shrinking)
• short fluid life due to poor oxidation performance
• shorter transmission life
• fuel economy degradation.
Figures 2 and 3 illustrate examples of thermal distress and excessive oxidation.
WHAT TO LOOK FOR IN A QUALITY ATF
Table 2 offers guidelines on what to look for in a
quality ATF product.
HOW TO DETERMINE THE CORRECT ATF
A good general rule of thumb for selecting the appropriate ATF is to use the specified fluid recommended by the OEM, particularly where warranty
may be considered.
TMC also recommends working with your oil supplier
for the correct fluid selection. It is good practice to re-
Proposed RP 1429 (T) Ballot Version—
TABLE 2:
WHAT TO LOOK FOR IN A QUALITY ATF
Property
What to look for:
Color
Should be dyed red.
Viscosity @ 100 C
Should be between 5.5 – 7.7 cSt (centiStokes).
Brookfield Viscosity @ -40 C
Should be less than 20,000 cP (centipoise) It is
preferred to be less than 13.000 cP.
20 hour KRL Shear Stability
20 PVL (Percent Viscosity Loss) maximum.
Application Claims from Fluid Supplier
Look for the claim that fluid is applicable to the
specific component (transmission) in use.
Refer to owner’s manual for OEM recommendations which are based on their specification.
Supporting Data / Cost
Should have test results available for the claims
advertised.
Proof of performance in field or fleet test(s).
Appropriate value for claims.
quest test data / credentials for use with multi-vehicle
ATF fluids which are generally classified as suitable
for use type fluids and are not generally approved
or endorsed by the OEMs.
© 2013—TMC/ATA
ATF’s should NEVER be mixed. A simple drain and
refill will result in mixed products. This could result in
a catastrophic transmission failure. When changing
products, TMC recommends that a thorough flush of
the transmission and cooler circuit be completed.
Proposed RP 1429 (T) Ballot Version—