The oil cooler is placed in the cooling water path to control the temperature of the lubricant using the temperature of the cooling water. When the lubricant temperature is high, cooling by cooling water, when the engine starts, the heat absorption from the cooling water so that the lubricant quickly increase the temperature. The oil cooler consists of a shell, a front cover, a rear cover and a copper core tube cast by an aluminum alloy. In order to enhance cooling, the tube is also set up a heat sink. Cooling water flows outside the tube, the lubricant flows through the tube, and the two heat exchange. There is also a structure that allows the oil to flow outside the tube, while the water flows in the pipe.