Patent ID: 7312185

Claim:
A grease composition for lubricating a rock bit for drilling subterranean formations or for lubricating a high temperature bearing, the grease comprising: a high viscosity index polyalphaolefin base fluid, wherein the polyalphaolefin contains an average of 30 to 100 carbon atoms, a branching ratio of less than about 0.19, and an average side chain length of 8 or more carbon atoms, wherein the high viscosity index polyalphaolefin base fluid comprises from about 15 wt. % to about 85 wt. % of the grease composition; an additional base fluid selected from the group consisting of monosubstituted alkyl naphthalenes, polysubstituted alkyl naphthalenes, and mixtures thereof, wherein the alkyl comprises from about 16 to about 30 carbon atoms, wherein the additional base fluid comprises from about 15 wt. % to about 85 wt. % of the grease composition; an ester base fluid, the ester comprising from about 5 to about 20 carbon atoms, wherein the ester base fluid comprises from about 0.5 wt. % to about 5 wt. % of the grease composition; a metal complex soap, the soap comprising a residue of one or more fatty acids comprising from 2 to 22 carbon atoms, wherein the metal is selected from the group consisting of calcium, lithium, sodium, barium, titanium, and mixtures thereof, wherein the metal soap comprises from about 5 wt. % to about 45 wt. % of the grease composition; an antioxidant, wherein the antioxidant comprises from about 0.2 wt. % to about 2 wt. % of the grease composition; a metal deactivator, wherein the metal deactivator comprises from about 0.1 wt. % to about 1.5 wt. % of the grease composition; an antiwear agent, wherein the antiwear agent comprises from about 0.1 wt. % to about 15 wt. % of the grease composition; and a bismuth oxide extreme pressure additive, wherein the bismuth oxide extreme pressure additive comprises from about 1 wt. % to about 20 wt. % of the grease composition.