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This paper describes the final chapter of the military specifications for aviation piston engine lubricants. The adoption and evolution of the Society of Automotive Engineers (SAE) Standards J1966 and J1899 from their initial development in 1991 to the present is reviewed. It includes the fine-tuning and revisions of the technical requirements derived from experience gained in qualification programs conducted. Also included are notes regarding the overall commercial oil qualification process and the remaining role of the U.S. Navy for military use approvals

In the early 1960's the U.S. Military began to gradually phase-out piston engined aircraft from it's inventory in favor of gas turbine powered aircraft. The emphasis of the aviation industry on the development of the new gas turbine engines and their attendant new synthetic lubricants resulted in the rapid decline of new oil development for aviation piston engines. As a result of this change in focus by the military and commercial engine builders, the maintenance of the MIL-L-6082 and MIL-L-22851 specifications also diminished. After years of decline, commercial interest in these specification products again developed. This paper is an attempt to document the rational used in modernizing these two specifications.

Although present performance of aircraft gas turbine engine lubricants is satisfactory, two major areas have been targeted for improvement: static bearing corrosion and thermal stability of the oil. Trends in future engine designs indicate that waste heat rejection will be the limiting factor in the development of high temperature lubricants. Field experience has shown that present performance of aircraft gas turbine engine lubricants in helicopter gearbox systems is marginal. A three-phase program has been initiated to develop a separate lubricant with improved load-carrying capacity and corrosion inhibition. Future design requirements will have to incorporate new materials and lubricants concurrently.