MIL-PRF-25478C, PERFORMANCE SPECIFICATION: COOLERS, LUBRICATING OIL, AIRCRAFT, GENERAL SPECIFICATION FOR (29 DEC 1997) {SUPERSEDING MIL-C-25478B]., This is the general specification for aircraft engine lubricating oil coolers that provide oil temperature regulation for aircraft gas turbine engines using high temperature synthetic base lubricating oil, and aircraft piston engines, turbo propeller gear boxes, and helicopter transmission gear boxes using petroleum based oil.