A fuel oil composition, characterized in that it has a density at 15 DEG C of 0.60 to 0.72 g/cm<3>, a surface tension at 20 DEG C of 170 to 250 DOLLAR (g)mN/cm and an octane value of 70 or more, and can be used both in a direct-injection gasoline engine and in a fuel cell. The fuel oil composition is free from the adverse effect on a reforming catalyst and an fuel cell electrode when used in a fuel cell, and does not damage driving characteristics when used in a direct-injection gasoline engine.
