The invention provides an engine for a vehicle which can easily execute a replacing work of an oil filter or an oil cooler. The vehicle engine is provided with a crank case, a cylinder head having an exhaust passage outlet in a front face, an oil pan being independently formed from the crank case and attached to a lower surface of the crank case, an oil supply path communicating the oil pan with of lubricated positions of the engine so as to circulate oil in the oil pan, an oil pump drawing the oil from the oil pan and pressure feeding the oil to the lubricated positions via the oil supply path, and an oil filter or an oil cooler interposed in the middle of the oil supply path and attached to a front face, a side face or a rear face of the oil pan.