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For existing fleets such as the U.S. military ground vehicle fleet, there are few ways to reduce vehicle fuel consumption that don’t involve expensive retrofitting. Replacing standard lubricants with those that can achieve higher vehicle efficiencies is one practical and inexpensive way to improve fleet fuel efficiency. In an effort to identify axle gear lubricants that can reduce the fuel consumption of its fleet, the U.S. Army is developing a stationary axle efficiency test stand and procedure. In order to develop this capability, on-track vehicle fuel consumption testing was completed using light, medium, and heavy tactical wheeled vehicles following a modified SAE J1321 type test procedure. Tested lubricants included a baseline SAE 80W-90, a fuel efficient SAE 75W-90, and a fuel efficient SAE 75W-140. Vehicle testing resulted in reductions in fuel consumption of up to 2%.

This paper examines sources and contributions of friction in heavy-duty diesel engines. Current and past work done on the characterization of diesel engine friction will be reviewed. It is also a goal to analyze each component system from a basic mechanics viewpoint highlighting some of the key friction producing phenomena. Different regimes of lubricated friction will be illustrated using a generic Stribeck diagram, with a focus on loading and relative velocities. Part II of this study will review lubricant effects on individual engine component friction as well as present data generated using commercial and military qualified lubricants in various bench tests, fired engine screening tests, and a modified version of the SAE J1321 Fuel Consumption Test using Army equipment.