A new class of high-temperature fluids, designated PR-143, which are capable of use in the range of −50 to −700 F, is discussed. These fluorinated materials do not sludge or tar on high-temperature exposure, even in the presence of air. The fluids are being tested in hydraulic systems, as gas turbine engine oils and as base fluids for high-temperature greases (designated PR-240). Properties and test results related to these applications are given.Presented as an American Society of Lubrication Engineers paper at the Lubrication Conference held in San Francisco, Calif., October 18–20, 1965.