A rolling bearing (1) includes an outer ring (2), an inner ring (4), and a plurality of rolling elements (6) arranged between the outer and inner ring (2, 4). The rolling bearing (1) is provided with lubricant. The outer ring (2) has an outer contact width (b.sub.o) between the outer ring (2) and the rolling elements (6). The inner ring (4) has an inner contact width (b.sub.i) between the inner ring (4) and the rolling elements (6). A ratio =b.sub.i/b.sub.o between the inner and outer contact width (b.sub.i, b.sub.o) is larger than 1.65 or a ratio =b.sub.i/b.sub.o between the inner and outer contact width (b.sub.i, b.sub.o) is larger than 0.97 and smaller than 1.06 or a ratio =b.sub.i/b.sub.o between the inner and outer contact width (b.sub.i, b.sub.o) is smaller than 0.68.

Provided is a grease containing a base oil and a hydrophilic nanofiber, the hydrophilic nanofiber having a thickness (d) of 0.01 to 500 nm being dispersed therein. The grease is low in an environmental load and excellent in safety on the human body and also has an appropriate worked penetration and has a high dropping point, and therefore, it is also excellent in heat resistance.

Provided is a lubricating oil composition for an internal combustion engine containing: (A) a lubricant base oil with a kinematic viscosity at 100 C. of 2.0 mm.sup.2/s to 5.0 mm.sup.2/s; (B) 50 mass ppm to 2000 mass ppm of a molybdenum-based friction modifier based on the total amount of the composition as an amount of molybdenum; (C) a nitrogen-containing ashless friction modifier; (D) a succinimide or a derivative thereof as a dispersant; (E) an amine ashless antioxidant as an antioxidant; and (F) 1000 mass ppm to 2200 mass ppm of a metallic detergent based on the total amount of the composition as an amount of metal, wherein the amount of sulfated ash in the composition is 0.9 mass % or less, and a nitrogen management index is 0.60 or less. Provided is a lubricating oil composition for an internal combustion engine having improved fuel efficiency and oxidative stability, while maintaining low amount of sulfated ash.

A rolling bearing (1) includes an outer ring (2), an inner ring (4), and a plurality of rolling elements (6) arranged between the outer and inner ring (2, 4). The rolling bearing (1) is provided with lubricant. The outer ring (2) has an outer contact width (b.sub.o) between the outer ring (2) and the rolling elements (6). The inner ring (4) has an inner contact width (b.sub.i) between the inner ring (4) and the rolling elements (6). A ratio =b.sub.i/b.sub.o between the inner and outer contact width (b.sub.i, b.sub.o) is larger than 1.65 or a ratio =b.sub.i/b.sub.o between the inner and outer contact width (b.sub.i, b.sub.o) is larger than 0.97 and smaller than 1.06 or a ratio =b.sub.i/b.sub.o between the inner and outer contact width (b.sub.i, b.sub.o) is smaller than 0.68.