and polyetherether ketone, the refrigerating oil comprising a base oil consisting essentially of an ester represented by the formula: R1 ???CH2 ???C???(CH2 ???OCOR2)3 ( 2) wherein R1 is an alkyl group having 1 to 3 carbon atoms, and R2 is a straight or branched chain alkyl group having 5 to 12 carbon atoms, said oil having a viscosity at 40??? C. of 2 to 70 cSt and a