Provided is a lubricating grease used for lubricating mechanical elements having a reciprocating sliding ball interposed therebetween and maintaining flaking resistance even under a high load in mechanical elements having a reciprocating sliding ball interposed therebetween. The present invention therefore provides a grease composition comprising a base oil (a), a diurea compound (b), an amide compound (c), and a thiophosphorous compound or a thiophosphoric acid ester compound (d), wherein the diurea compound (b) includes a compound represented by Formula (1) R.sub.1—NHCONH—R.sub.2—NHCONH—R.sub.3 (1) wherein R.sub.1 and R.sub.3 represent an acyclic aliphatic hydrocarbon group having from 8 to 20 carbon atoms, and R.sub.2 represents a diphenylmethane group.

Lubricating oil compositions are disclosed. The lubricating oil compositions include one or more base oils (A) containing one or more polyalphaolefin (PAO) base oils derived at least in part from a C.sub.12 olefin. The lubricating oil compositions further include from about 65 wt. % to about 85 wt. %, based on the total weight of the lubricating oil composition, of one or more base oils (B) having a kinematic viscosity at 100° C. of from about 3.0 cSt to about 5.5 cSt; and from about 0.1 wt. % to about 10 wt. %, based on the total weight of the lubricating oil composition, of a succinimide dispersant.

Lubricating oil compositions are disclosed. The lubricating oil compositions include one or more base oils (A) containing one or more polyalphaolefin (PAO) base oils derived at least in part from a C.sub.12 olefin. The lubricating oil compositions further include from about 65 wt. % to about 85 wt. %, based on the total weight of the lubricating oil composition, of one or more base oils (B) having a kinematic viscosity at 100° C. of from about 3.0 cSt to about 5.5 cSt; and from about 0.1 wt. % to about 10 wt. %, based on the total weight of the lubricating oil composition, of a succinimide dispersant.

Provided is a grease composition for a ball joint that can reduce the wear of a ball seat at a slide region and also has excellent compatibility with a dust cover. The grease composition for a ball joint comprises a base oil, a thickener, and an additive. The base oil contains an ethylene-α-olefin copolymer and the kinetic viscosity of the base oil at 40° C. is 2,000 to 6,000 mm.sup.2/s. The additive contains a polar wax (e.g., monoamide wax or ester wax).

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.

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.

There is provided a grease composition for improving the chemical stability of the grease composition and increasing the fatigue life of a member in which the grease composition is used. The problems can be solved by a grease composition including a poly-α-olefin; a urea-based thickener; molybdenum dithiophosphate; and barium sulfonate, wherein a difference between an SP value of the urea-based thickener and an SP value of the poly-α-olefin is 3.5 or less.

There is provided a grease composition for improving the chemical stability of the grease composition and increasing the fatigue life of a member in which the grease composition is used. The problems can be solved by a grease composition including a poly-α-olefin; a urea-based thickener; molybdenum dithiophosphate; and barium sulfonate, wherein a difference between an SP value of the urea-based thickener and an SP value of the poly-α-olefin is 3.5 or less.

The invention discloses a lubricating grease with thixotropy and a preparation method thereof. The lubricating grease comprises a polyurea/high base number calcium sulfonate composite thickener, colloidally dispersed calcium carbonate solid particles in the form of calcite, a calcium borate or calcium borate composite, and a calcium soap of fatty acid having 12 to 24 carbon atoms. The above components are uniformly dispersed in an oil phase medium. The content of high base number calcium sulfonate in the lubricating grease is less than 22 wt %.

An object is to provide a grease composition for a ball joint capable of reducing the starting torque, reducing the operating torque, and improving the low temperature property as compared with the related art. The grease composition for a ball joint according to the present invention contains a silicone oil as a base oil and an additive, and contains an amino-modified silicone and a modified polyolefin as the additive. The silicone oil preferably includes at least one of dimethyl silicone oil and phenyl-modified silicone oil.