Engine oil serves to cool, clean and lubricate all the internal moving parts of the engine like piston pin, cylinder walls, valves, cylinder rings, crankcase and gear train. These must be kept oiled to keep the vehicle running smoothly and effectively on the roads. Engine parts when well-oiled will run smoothly, and hence make the engine run better and increase its life too. Without oil, engine will quickly deteriorate as overheating, grim and continual friction will wear down or damage parts, clog hoses and erode valves etc.
