The invention provides a lubricating oil composition comprising a lubricating base oil with a kinematic viscosity at 100° C. of 1-10 mm2/s, a % Cp; of 70 or greater and a % CA of no greater than 2 and a viscosity index improver having a weight-average molecular weight of 100,000 or greater and a ratio of weight-average molecular weight to PSSI of 1.0×104 or greater, at 0.1-50% by mass based on the total amount of the composition, and having a kinematic viscosity at 100° C. of 9.0-12.5 mm2/s and a HTHS viscosity at 150° C. of 2.8 mPa·s or greater. It further provides a lubricating oil composition comprising a lubricating base oil with a kinematic viscosity at 100° C. of 1-6 mm2/s, a % Cp of 70 or greater and a % CA of no greater than 2, a hydrocarbon-based viscosity index improver with a PSSI of no greater than 20, and a poly(meth)acrylate-based viscosity index improver.