Disclosed is a synthetic oil useful as a base stock for jet engine lubricating oils. The initial viscosity of the synthetic oil at 210.degree.F. is 5.0-5.5 centistokes and at -40.degree.F. is less than 13,000 centistokes. Furthermore, it does not freeze when held at -40.degree.F. for 72 hours. The oil comprises a blend of (1) a pentaerythritol ester product consisting essentially of pentaerythritol material completely esterified by straight chain C.sub.4 -C.sub.10 alkanoic acid material, and (2) a trimellitate ester product consisting essentially of trimellitic acid completely esterified by C.sub.4 -C.sub.13 alkanol material. The weight ratio of the trimellitate ester product to the pentaerythritol ester product is generally in the range from about 1:10 to about 1:1.