Provided is a lubricating oil composition capable of revealing fuel consumption reducing properties due to a friction reducing effect within a short period of time while having excellent fuel consumption reducing properties, specifically a lubricating oil composition of the present invention includes a base oil, a molybdenum dithiocarbamate, a calcium detergent, a magnesium detergent, and a boron-free succinimide, wherein the content of the molybdenum dithiocarbamate as converted into a molybdenum atom is 1,200 ppm by mass or less on a basis of the whole amount of the composition; the content of the boron-free succinimide as converted into a nitrogen atom is less than 1,200 ppm by mass on a basis of the whole amount of the composition; and a mass ratio of the molybdenum atom (Mo) to a magnesium atom (Mg) of the magnesium detergent [Mo/Mg] is 0.1 or more.