The US Army is currently assessing the feasibility and defining the requirements of a Single Common Powertrain Lubricant (SCPL). This new lubricant would consist of an all-season (arctic to desert), fuel-efficient, multifunctional powertrain fluid with extended drain capabilities. As a developmental starting point, diesel engine testing has been conducted using the current MIL-PRF-46167D arctic engine oil at high temperature conditions representative of desert operation. Testing has been completed using three high density military engines: the General Engine Products 6.5L(T) engine, the Caterpillar C7, and the Detroit Diesel Series 60. Tests were conducted following two standard military testing cycles; the 210 hr Tactical Wheeled Vehicle Cycle, and the 400 hr NATO Hardware Endurance Cycle. Modifications were made to both testing procedures to more closely replicate the operation of the engine in desert-like conditions. These modifications included operation at elevated oil sump (nominally 127°C) and water jacket (nominally 96°C) temperatures. Test engines completed an initial tear down, inspection, and metrology process prior to being built to manufacturer-supplied specifications for testing. After completion of testing all engines were again disassembled and underwent a complete metrology and component-rating process to determine overall engine wear and deposits. Results to date have shown promising data for use of low viscosity crankcase lubricants utilized at high temperatures in US Army diesel engines.