U.S. Environmental Protection Agency +
Low-Viscosity Lubricants
A Glance at Clean Freight Strategies
Gallons Saved:
CO2 Savings:
metric tons
Fuel Cost Savings:
Fuel Economy Increase:
MPG (originaL 6 mpg):
Synthetic lubricants in the engine crankcase, rear axle, and transmission can improve
fuel economy by about 3 percent, saving nearly 485 gallons of fuel and eliminating
5 metric tons of greenhouse gas emissions for a typical combination truck each year.
Lubricants reduce friction and wear of critical vehicle systems including the engine,
transmission and drive train. Without lubricants, the moving parts inside these systems
would grind together, causing heat, stress and wear. Conventional mineral oil lubricants
may have too high viscosity (internal friction that resists sliding and inhibits flow) to
effectively slip between and lubricate the moving parts of these systems, particularly
in newer truck components that are designed with close tolerances and tight fits.
Conventional lubricants may also be heavy, making it harder for pumps, gears and
shafts to move. These effects create energy losses and friction losses, and waste fuel.
Low-viscosity Lubricants are less resistant to flow than conventional lubricants, a
property that helps reduce friction and energy losses. Depending upon the application,
low-viscosity lubricants may also contain additives designed to withstand the extreme
pressure (EP) that could occur as the lubricant flows between tight-fitting parts.
Low-viscosity lubricants may be made from synthetic or mineral oil blends with
low-viscosity and EP additives. Manufacturers generally offer low-viscosity blends
as "fuel economy" lubricants, since the fuel-saving potential of these products is
significant. A national trucking association reports that synthetic transmission and
axle lubricants can improve fuel economy by 0.5 % in the summer and 2 percent in
the winter (viscosity is temperature-dependent). A paper published by a professional
engineering society found that synthetic engine and transmission lubricants could
improve fuel economy by 5 percent, with greater gains at lower speeds. Another paper
from this same organization reports that synthetic gear lubricants can improve fuel
economy by about 3 percent. European research demonstrates a 3 to 5 percent gain
in truck fuel economy using low friction engine lubricants and a 1 to 4 percent gain
using low friction transmission lubricants.
Synthetic and semi-synthetic lubricants typically cost more than conventional mineral
oil lubricants. Truck service stations suggest that semi-synthetic oils cost about 50
percent more than conventional mineral oils. However, for most trucks, the fuel cost
savings generally outweigh the higher product cost. Furthermore, synthetic lubricants
may extend the interval between lubricant changes therefore further reducing costs
of truck fleets.
EPA-420-F-19-027 | August 2019 | SmartWay Transport Partnership | epa.gov/smartway

Low-Viscosity Lubricants: A Glance at Clean Freight Strategies (continued)
The combined effect of low-viscosity synthetic engine oils
and drive train lubricants can improve fuel economy by at least
3 percent, saving nearly 485 gallons of fuel per year for a
typical combination truck. Even with the higher cost of the
synthetic oil, truck owners can save more than $1,410 in
fuels per year. Additional cost savings may be possible due
to reduced wear and maintenance. Switching to low-viscosity
lubricants will reduce greenhouse gas emissions by 4.9 metric
tons per year for each truck.
Gallons of
fuel saved
per year

Trucking companies should consider using Low-viscosity Lubricants to improve fueL economy. Synthetic
oiLs are compatible with most truck systems, save fuel, and should provide net cost savings.
Before switching lubricants, trucking companies should ensure that the product suits the intended
application. Always check manufacturer specifications before switching engine, transmission or drive
train lubricants.
Consult the manufacturer's vehicle and parts owner manuals and service manuals for information and
recommendations on lubrication specifications and procedures. Lubricating oil manufacturers and
lubrication guides can provide information about product applications.
Trucking associations, equipment manufacturer associations and trucking industry publications may
provide additional information and case studies about the benefits and uses of various lubricants.

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