The US Army is currently seeking to reduce fuel consumption by utilizing fuel efficient lubricants in its ground vehicle fleet. An additional desire is for a lubricant which would consist of an all-season (arctic to desert), fuel efficient, multifunctional Single Common Powertrain Lubricant (SCPL) with extended drain capabilities. To quantify the fuel efficiency impact of a SCPL type fluid in the engine and transmission, current MIL-PRF-46167D arctic engine oil was used in place of MIL-PRF-2104G 15W-40 oil and SAE J1321 Fuel Consumption In-Service testing was conducted. Additionally, synthetic SAE 75W-140 gear oil was evaluated in the axles of the vehicles in place of an SAE J2360 80W-90 oil. The test vehicles used for the study were three M1083A1 5-Ton Cargo vehicles from the Family of Medium Tactical Vehicles (FMTV). The M1083 utilizes a Caterpillar C7 ACERT engine, an Allison MD3070PT 7-speed automatic transmission, and Rockwell/Arvin-Meritor 7.8:1 ratio, single reduction, amboid gearing, bevel wheel end reduction axles. Each test segment consisted of vehicle operation over a 67.6 km (42 mile) course at speeds of 40.2 and 80.4 km/hr (25 and 50 mph). These speeds where chosen to be representative of actual military vehicle usage in convoy type operations. Each test segment was compared to its previously run baseline for fuel consumption comparison. A fuel consumption improvement was demonstrated for reduced viscosity lubricants in both the engine and transmission test segments.