SmartWay Transport | EPA-420-F12-076 | www.epa.gov/smartway

Low-Viscosity Lubricants

A Glance at Clean Freight Strategies

Energy

and 

Fuel Savings

Gallons Saved 

= 

485 gallons

New MPG

(from 6.0 mpg)

= 

6.18 mpg

Fuel Cost Savings

= 

$1,680 

CO2 Savings 

= 

4.93 Metric tons

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.

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 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 percent 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.
Page 2

Low Viscosity Lubricants

SmartWay Transport | EPA-420-F12-076 | www.epa.gov/smartway

Savings and Benefits 

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 $1,680 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 

4.93 metric tons per year for each truck.

1 Trucking companies 

should consider using 

low-viscosity lubricants 

to improve fuel economy. 

Synthetic oils are com- patible with most truck 

systems, save fuel, and 

should provide net cost 

savings.

2 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.

3 Consult the manu- facturer’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.

Next Steps

.

4 Trucking associations, 

equipment manufacturer 

associations and truck- ing industry publications 

may provide additional 

information and case 

studies about the benefits and uses of various 

lubricants.