A common drawback of high-temperature oils based on pentaerythritol esters and C-5-C-9 synthetic fatty acids (SFA) is low resistance to oxidation in the presence of metals at high temperatures. In this respect, the possibility of increasing the temperature limit of the efficiency of pentaerythritol ester is being intensively investigated: by removal of contaminants that initiate oxidation; improvement of the production technology; addition of more thermostable components, usually oxidation inhibitors [1-4].