Lubricant composition

Abstract

Provided is a lubricant composition containing a lubricant base oil and 0.5 to 10 mass % of (A) an ethylene/α-olefin copolymer having a number average molecular weight of 2,800 to 8,000, in which the lubricant base oil used here has a kinematic viscosity at 100° C. of 1.5 to 40 mm 2 /s, a viscosity index of 100 or more, a pour point of −25° C. or lower, and a sulfur content of 0.01 mass % or less, and the lubricant composition has low viscosity and a long metal fatigue life, while being excellent in low-temperature fluidity and oxidation stability, thereby being particularly suitable as a lubricant for automobile transmissions or the like.

1 : A lubricant composition, comprising:
 a lubricant base oil; and   0.5 to 10 mass % of (A) an ethylene/α-olefin copolymer having a number average molecular weight of 2,800 to 8,000,   wherein said lubricant base oil has a kinematic viscosity at 100° C. of 1.5 to 40 mm 2 /s, a viscosity index of 100 or more, a pour point of −25° C. or lower, and a sulfur content of 0.01 mass % or less.   
   
   
       2 : The lubricant composition according to  claim 1 , further comprising 0.01 to 2.0 mass % of an extreme pressure agent (B) selected from the group consisting of a phosphorus-based extreme pressure agent, a sulfur-based extreme pressure agent, and a mixture thereof, the component (B) having a total sulfur content of 0.15 mass % or less. 
   
   
       3 : The lubricant composition according to  claim 2 , further comprising (C) at least one kind of an additive selected from the group consisting of: an antioxidant; another extreme pressure agent; a wear-resisting agent; an oiliness agent; a detergent dispersant; and a pour point depressant. 
   
   
       4 : A lubricant for automobile transmissions comprising the lubricant composition according to  claim 1 .