An object of the present invention is to provide a grease composition which has little influence on the environment and has good rust prevention and water resistance against salt water such as sea water. The grease composition comprises a biodegradable base oil and a rust-preventive agent comprising a calcium sulfonate complex and a sorbitan fatty acid ester, wherein a total content of biodegradable organic substances in the grease composition is 75% by mass or more, and wherein a content of the rust-preventive agent is 2.5 to 30% by mass.

A grease composition includes base oil, a thickener, and an inorganic additive. The base oil is a poly--olefin having a base oil kinematic viscosity of 15 to 50 mm.sup.2/s at 40 C. The thickener is a diurea expressed by Structural Formula (1). The content of the thickener is 10 to 22 mass % with respect to the total amount of the base oil and the thickener. The inorganic additive is a mixture containing sepiolite and bentonite, and is organically modified. The content of the inorganic additive is 2 to 20 mass % with respect to the total amount of the base oil and the thickener.
R.sup.1NHCONHR.sup.2NHCONHR.sup.3(1)

The present invention provides a grease composition for constant-velocity joints comprising (a) a base oil, (b) a diurea thickener, (c) molybdenum dithiocarbamate, (d) molybdenum dithiophosphate, (e) overbased calcium sulfonate, and (f) neutral zinc sulfonate. The composition of the present invention is excellent in durability at high temperature and vibration suppression.

A grease composition includes a base oil, a thickener, and polymethyl methacrylate particles. The base oil is a poly--olefin. The polymethyl methacrylate particles have an average particle size of 2 m to 7 m. A content of the polymethyl methacrylate particles is 10% by mass to 20% by mass with respect to a total amount of the base oil and the thickener.

A grease composition includes a base oil, a thickener, and zirconium oxide particles. The base oil is a poly--olefin. The zirconium oxide particles have a median diameter D.sub.50 of 0.6 m to 4 m. A content of the zirconium oxide particles is 2% by mass to 15% by mass with respect to a total amount of the base oil and the thickener.

The invention provides a grease composition used for lubricating a mechanical part having a steel portion to be lubricated which performs a rolling motion and a rolling and sliding motion, containing a base oil, a thickener and an additive, wherein the additive includes at least one compound selected from the group consisting of polyethylene wax, oxidized polyethylene wax, polypropylene wax, montan wax and amide wax.

The present invention provides a grease composition for constant velocity joints, which includes a lubricating base oil, a thickener including a nitrogen-containing compound, a triglyceride, a diester, and a boron nitride, wherein a total content of the triglyceride and the diester is 1 to 5 mass % based on a total amount of the grease composition, and a mass ratio of a content of the triglyceride to a content of the diester (triglyceride/diester) is 0.3 to 1.5.

The object of the present invention is to provide a foreign substance removing lubricant composition having high foreign substance removing effects and being capable of improving the lubricating properties as compared to conventional lubricant compositions, a foreign substance removing lubricant composition applied member, and a method for using the foreign substance removing lubricant composition. The foreign substance removing lubricant composition of the present invention comprises a perfluoroalkyl group containing compound (S) having a perfluoroalkyl group or a fluoropolyether containing compound. As a result, foreign substance removing effects can be enhanced, and the lubricating properties can be improved as compared to the conventional lubricant compositions.

A lubricant composition according to the present invention contains a fatty acid metal salt, a metal dithiocarbamate, and an additive having an effect of increasing an acid value of the lubricant composition, whereby fretting resistance performances are further improved.

The rolling bearing of the present invention is lubricated with a lubricant composition which contains a fatty acid metal salt, a metal dithiocarbamate, a phosphorous-type additive, and a basic additive, and which has a total acid value of 3.7 mgKOH/g or more. The rolling bearing makes it possible to further improve anti-fretting performance, and to reduce a decrease in fretting resistance even when used under the circumstance that fluorine-type grease penetrates into the bearing using urea-type grease.