The present invention provides a mineral base oil having a kinetic viscosity at 100°C of 7 mm 2 /s or more and less than 10 mm 2 /s, a viscosity index of 100 or more, and a temperature gradient Δ|η*| complex viscosity between two temperature points of -5°C and -15°C of 240 mPa·s/°C or less as measured with a rotary rheometer at an angular velocity of 6.3 rad/s. The use of the mineral base oil enables easy preparation of a lubricating oil composition and a grease composition having excellent oxidation stability while ensuring the freedom of selection of additives.