Patent ID: 8119579

Claim:
A method of formulating a lubricating oil composition comprising a major amount of a base oil of lubricating viscosity and an effective amount of at least one lubricant antioxidant and wherein said base oil consists essentially of a blend of a Group III oil derived from synthesis gas and a Group IV oil, the improvement comprising using a blend of (i) a Group III oil containing at least 90% of a mixture of branched (paraffins having a chain length of about C 20 to C 40 , a molecular weight of about 280 to about 562 and a pour point of less than −18° C., and (ii) Group IV oils having a Kv from about 2 to about 15 cSt at 100° C., wherein said oils are blended in a ratio such that the lubricating composition exhibits an oxidative stability determined by a measure of high temperature deposits formed in TEOST Test MH T-4 (ASTM D7097) that is less than half the mathematical sum of the oxidative stability determined for each of unblended Group III and Group IV oils containing the same antioxidant in the same amount as in the blend, and wherein the antioxidant is present in an amount in said blend whereby the composition has high temperature deposits of about 5 to 20 when measured by said TOEST Test, thereby providing a lubricating composition with enhanced oxidative stability.