A slant engine for a utility engine which a cylinder is attached to the crankcase with slanted with respect to the a rotational direction of a crankshaft, comprises a reservoir oil tank formed outside of the crankcase at lower portion for reserving lubricant, a communication pipe connected to bottom portions of the reservoir oil tank and the crankcase for communicating the lubricant in the crankcase and the reservoir oil tank, and a vent pipe connected to both of the reservoir oil tank and the inside of the crankcase.