MIL-PRF-8188D, PERFORMANCE SPECIFICATION, CORROSION-PREVENTIVE, AIRCRAFT TURBINE ENGINE, SYNTHETIC BASE (10 DEC 1997) [SUPERSEDING MIL-C-8188C]., This specification covers the requirements for one type of corrosion-preventive oil for preservation of engines which normally operate on synthetic base oils. This oil is identified by NATO Code Number C-638..