Mineral base oil, lubricant composition, internal combustion engine, lubricating method of internal combustion engine

Provided is a mineral base oil satisfying the following requirements (I) to (III):Requirement (I): a kinematic viscosity at 100° C. is 2 mm2/s or more and less than 7 mm2/s;Requirement (II): a viscosity index is 100 or more; andRequirement (III): a temperature gradient Δ|η*| of complex viscosity between two temperature points −10° C. and −25° C. is 60 Pa·s/° C. or less as measured with a rotary rheometer under conditions at an angular velocity of 6.3 rad/s and a strain amount of 0.1 to 100%.The foregoing mineral base oil can become a lubricating oil composition having desirable low-temperature viscosity characteristics, including low-temperature fuel consumption and low-temperature engine start-up performance, and also having excellent high-temperature piston detergency.