Lubricant composition

A lubricating oil composition comprising:

• a lubricating base oil having a kinematic viscosity at 100° C. of 1-6 mm2/s, a % Cp value of 70 or greater and a % CA value of no greater than 2, and
• a viscosity index improver which, when added to the lubricating base oil, results in an A/B ratio of less than 3.2 between the thickening effect A on the kinematic viscosity at 100° C. represented by the following formula (1) and the thickening effect B on the HTHS viscosity at 150° C. represented by the following formula (2), and a C/B ratio of less than 1.5 between the thickening effect C on the HTHS viscosity at 100° C. represented by the following formula (3) and the thickening effect B on the HTHS viscosity at 150° C. represented by the following formula (2):
• A=X−X0 (1)
• wherein A represents the thickening effect on the kinematic viscosity at 100° C., X represents the kinematic viscosity at 100° C. by mm2/s of a mixture of the lubricating base oil and the viscosity index improver at 3% by mass, and X0 represents the kinematic viscosity at 100° C. by mm2/s of the lubricating base oil,
• B=Y−Y0 (2)
• wherein B represents the thickening effect on the HTHS viscosity at 150° C., Y represents the HTHS viscosity at 150° C. by mPa·s of a mixture of the lubricating base oil and the viscosity index improver at 3% by mass, and Y0 represents the HTHS viscosity at 150° C. by mPa·s of the lubricating base oil,
• C=Z−Z0 (3)
• wherein C represents the thickening effect on the HTHS viscosity at 100° C., Z represents the HTHS viscosity at 100° C. by mPa·s of a mixture of the lubricating base oil and the viscosity index improver at 3% by mass, and Z0 represents the HTHS viscosity at 100° C. by mPa·s of the lubricating base oil.