Grease composition

A grease composition to be enclosed in an outer ring rotation type rolling bearing for use in automotive electric auxiliary machines,

• said grease composition consisting of base oil, a thickener, a peeling-resistant additive, a wear-resistant additive, a rust-preventive agent, and other additives,
• wherein said base oil is mixed oil of trimellitic acid ester oil and poly-α-olefin oil mixed therewith in a mass ratio of (80:20) to (90:10),
• said trimellitic acid ester oil has a kinematic viscosity of 40 to 140 mm2/s at 40 degrees C. and a pour point of not more than −35 degrees C.;
• and said poly-α-olefin oil has a kinematic viscosity of 10 to 60 mm2/s at 40 degrees C. and a pour point of not more than −50 degrees C.,
• said thickener consists of a diurea compound shown by a formula (1) shown below
• [chemical formula 1]
• R1—NHCONH—R2—NHCONH—R1 (1)
• wherein R2 denotes a divalent aromatic hydrocarbon group having a carbon number of 6 to 15, and R1 denotes a cyclohexyl group
• wherein said thickener is contained in said grease at 5 to 25 mass % for a whole amount of said grease composition,
• said peeling-resistant additive consists of at least one molybdate alkaline metal salt selected from among sodium molybdate, potassium molybdate, and lithium molybdate and is contained at 0.1 to 1.5 mass % for a whole amount of said grease composition,
• said wear-resistant additive consists of zinc dialkyldithiophosphate and is contained at 0.1 to 2.0 mass % for a whole amount of said grease composition,
• said rust-preventive agent is contained at 0.5 to 5.0 mass % for a whole amount of said grease composition, and
• said other additives are contained at not more than 0.3 mass % for a whole amount of said grease composition.