Abstract: A lubricating grease is specific for a rock bit for drilling subterranean formations. The rock bit body includes a plurality of journal pins, each having a bearing surface, with a cutter cone mounted on each journal pin and also including a bearing surface. A grease reservoir provides lubricating grease to such bearing surfaces. The grease composition adjacent the bearing surfaces comprises a lubricating base oil, sufficient thickener and additives in the base oil to form a rock bit grease, and an effective amount of polarized graphite.

Abstract: A rock bit for drilling subterranean formations is lubricated with a grease composition made from a high-viscosity synthetic lubricant basestock and a combination of lubricant additives. The grease composition preferably has in the range of from 1 to 20 percent by weight polyisobutylene, in the range of from 50 to 90 percent by weight ethylene-alphaolefin, up to approximately 40 percent by weight polyalphaolefin, and in the range of from 4 to 45 percent by weight lubricant additives. The rock bit grease composition has a viscosity index in the range of from about 250 to 325, and has an absolute viscosity of greater than about 100,000 centipoise at a temperature of approximately 70.degree. F. and at a shear rate of less than about 40 seconds.sup.-1, without the use of solid metal-containing extreme pressure agents or thickening agents.

Abstract: A rock bit grease composition is prepared by combining synthetic polymer lubricant basestocks comprising a first ethylene-alphaolefin polymer having an average molecular weight in the range of from 3,500 to 4,000, and a polyisobutylene polymer to form a first master. A metal complex soap base thickener is prepared by combining a synthetic polymer lubricant basestocks comprising a second ethylene-alphaolefin having an average molecular weight in the range of from 400 to 800, with an alkali-metal or alkaline-earth metal hydroxide, and at least one fatty acid. A preferred fatty acid is a blend of a first fatty acid having in the range of from 15 to 20 carbon atoms, and a second fatty acid having in the range of from 5 to 12 carbon atoms. The first master and metal complex soap base thickener are mixed together in desired proportions.