Operational energy can be roughly defined to be the energy required to sustain military forces and weapons platforms for military operations. Energy is fundamental to the ability of U.S. military to project and sustain its military forces. For existing vehicle fleets there are few ways to reduce vehicle fuel consumption that don’t involve expensive retrofitting. Replacing standard lubricants with lubricants that reduce fuel consumption is one practical and inexpensive way to improve fleet fuel efficiency and reduce operational energy. In an effort to identify gear lubricants that can reduce the fuel consumption of its vehicle fleet, the U.S. Army is developing a stationary axle efficiency test stand and procedure. In order to develop this capability, in-service vehicle fuel consumption testing was completed on light, medium, and heavy tactical wheeled vehicles following a modified SAE J1321 test procedure. Lubricants tested included standard 80W-90, a fuel efficient SAE 75W-90, and a fuel efficient SAE 75W-140. Using the data from in-service vehicle testing and simulation, a stationary axle efficiency test stand was designed and built. The test stand was constructed in a modular fashion to be capable of fitting a variety of military axles. The test stand utilizes two internally regenerative 250 hp AC motors to provide input power and absorption, and uses shaft encoders and digital torque flanges to provide precise measurement of speed and load for power and efficiency calculations. Preliminary axle efficiency test stand results from the same 80W-90, 75W-90 and 75W-140 test oils used in the in-service SAE J1321 testing are included for light and medium tactical wheeled vehicle axles. Data presented includes efficiency maps and initial results from a military unique driving cycle which could form the basis of a federal test method and be used for the qualification of fuel efficient gear oil (FEGO) for military use.