An assessment of the performance of oils in Air Force turbine engines and helicopter gear boxes is presented along with predicted performance of current and upgraded military specification oils in advanced and “growth” engine designs. Data is presented on advanced ester base oils evolving from current research efforts. Future high temperature candidate oils representing the ultimate stability for turbine engines are also discussed. Their use, in most cases, entails engine design considerations to accommodate their unique properties. The advantages and disadvantages of the various classes of synthetic oils for turbine engines are discussed, and deficiencies are identified where additional research programs are needed.