| 摘要 |
A lubricant oil composition comprising: a lubricant base oil whose kinematic viscosity at 100° C. is 1 to 6 mm2/s, % Cp is not less than 70, and % CA is not more than 2; a first viscosity index improver in which the ratio A/B of a viscosity increasing effect A in the equation (1) to a viscosity increasing effect B in the equation (2) when added to the lubricant base oil is a value of not less than 4.5, and a PSSI is not more than 30; and a second viscosity index improver in which the ratio A/B when added to the lubricant base oil is a value less than 4.5: A=X−X0 (1) B=Y−Y0 (2) wherein A represents a viscosity increasing effect of the kinematic viscosity at 100° C., B represents a viscosity increasing effect of the HTHS viscosity at 150° C., X represents a kinematic viscosity at 100° C. of a mixture of the lubricant base oil with 3% by mass of the first or second viscosity index improver, X0 represents a kinematic viscosity at 100° C. of the lubricant base oil, Y represents an HTHS viscosity at 150° C. of a mixture of the lubricant base oil with 3% by mass of the first or second viscosity index improver, and Y0 represents an HTHS viscosity at 150° C. of the lubricant base oil.
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