High load-carrying turbo oils containing amine phosphate and thiosemicarbazide derivatives

This invention relates to synthetic based turbo oils, preferably polyol ester-based turbo oils which exhibit exceptional load-carrying capacity by use of a synergistic combination of sulfur (S)-based and phosphorous (P)-based load additives. The S-containing additives of the present invention are thiosemicarbazide and its derivative, and the P-containing component is one or more amine phosphates. The turbo oil composition consisting of the dual P/S additives of the present invention achieves an excellent load-carrying capacity, which is better than that obtained when each additive was used alone at a treat rate higher than or comparable to the total combination additive treat rate, and the lower concentration requirement of the P-based additive allows the turbo oil composition to meet U.S. Navy MIL-L-23699 requirement on the Si seal compatibility.