Schmieroel

A functional fluid (e.g. lubricant, hydraulic fluid or heat-exchange fluid) comprises at least one polyphenyl polyether having 4-7 benzene rings and 3 to 6 oxygen atoms, and a chelate of a heavy metal from Groups I to IV, VII or VIII of the Mendeleef Periodic table with a b -diketone having the general formula R-CO-CHZ-CO-R1 in which each of R and R1 is a C1- 9 alkyl group or a C6- 10 aryl, alkaryl or aralkyl group, and Z is hydrogen, a C1- 6 alkyl group, a C2- 6 carbalkoxy group, or an aryl, alkaryl or aralkyl group, the chelate being present in sufficient amount to improve the oxidation resistance of the polyether at temperatures of at least 550 DEG F. The chelate may be a metal acetylacetonate, and both the polyphenyl polyethers and the chelates are extensively exemplified.