Suitability of Military Specification Lubricants for Two-Stroke RPV Engines

The Army is exploring the feasibility of using Remotely Piloted Vehicles (RPV's) in a multi-mission role. Powerplants for these RPV's are to be small, two-stroke, air-cooled, reciprocating engines which require a fuel/oil mix for operation. As no federal or military specification lubricant exists for this application, this paper details results of an analytical/experimental investigation to evaluate the suitability of existing MIL SPEC lubricant classes for Army RPV use. Performance of a limited sampling of military specification lubricants was evaluated by cyclic testing with a small two-stroke, air-cooled piston engine currently used in the Army AQUILA RPV. An ashless dispersant lubricant qualified to Boating Industry of America standards for two-cycle, water-cooled engines (BIA/TC-W) was used for reference. Standard magneto ignition and engine cooling were used in 20 of the 23 tests. The final three tests explored the combined effects of capacitive discharge ignition and elevated cylinder head temperature.