Synthetic engine and drive train lubricants can improve fuel economy by about three percent, saving nearly 500

gallons of fuel and eliminating five metric tons of greenhouse gas emissions for a typical combination truck each

year.

What is the challenge?

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. .

What is the solution?

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 lowviscosity 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 percent

in the summer and two 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 five

percent, with greater gains at lower speeds. Another

paper from this same organization reports that

synthetic gear lubricants can improve fuel economy

by about three percent. European research

demonstrates a three to five percent gain in truck fuel

economy using low friction engine lubricants and a

one to four 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.

The results are in . . . 

The combined effect of low-viscosity synthetic engine

oils and drive train lubricants can improve fuel

economy by at least three percent, saving nearly 500

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 $500 per year.

Additional cost savings may be possible due to

reduced wear and maintenance. Switching to lowviscosity lubricants will reduce greenhouse gas

emissions by five metric tons per year for each truck.

Next steps

Trucking companies should consider using lowviscosity 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. Companies should also

consult 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.