Abstract: A grease for a bearing of a fan comprises a base oil selected from a various kinds of silicone oils having a viscosity of 30 to 500 mm2/s at 40 degree-C. and a viscosity of 30,000 mm2/s or less at −30 degree-C., and a diurea compound, as a thickening agent, at the compounding ratio of 2 to 30%-wt. The urea compound has a general formula of: R1—NHCONH—R2—NHCONH—R3 wherein R2 indicates a tolylene group, a diphenylmethan group or a dimethylbiphenylene group, and R1 and R3 respectively indicate a straight chain saturated alkyl group having the number of carbon atoms of 6 to 18, and an alicyclic group, and wherein the ratio of the straight chain saturated alkyl group to the alicyclic group is within a range of 5 to 95 mol-% to 95 to 5%-mol. The grease maintains its properties suitable for use in a fan, and effectively restrict or prevent generation of hoot sound, while providing satisfactory durability and cost-effctiveness.

Abstract: According to the present invention, PAO oil and ester oil are mixed in a ratio by weight of from 50:50 to 90:10 to provide a base oil having a viscosity of not more than 70 mm2/S at 40° C., to which base oil is then added 5-25% by weight of diurea, which is an alicyclic compound, serving as a thickener, and ZnDTC, which is an additive. The grease thus prepared is filled in a bearing 2. This bearing 2 is fitted in the inner portion of a pulley body 1 having a pulley peripheral surface is to be contacted by a belt driven by the engine of an automobile. Thereby, brittle peeling occurring in the raceway surfaces and ball surfaces, and abnormal noise under cold ambient can be reliably prevented.