Form This specification covers a fluorocarbon (FKM) rubber stock in the form of molded test slabs. Application Primarily for determining compatibility of the type of elastomer with various lubricating oils@ hydraulic fluids@ and fuels. Useful as a reference for evaluating compatibility to a variety of gas turbine engine oils@ including higher thermooxidative stability (HTS) lubricants@ including those conforming to MIL-PRF-23699 Class HTS@ MIL-PRF-7808 Grade 4 and AS5780 Class HPC@ at elevated temperature (392 ??/ 200 ??.