1.Attached to the bottom of the engine block is the oil pan, which seals in the lubricating oil for the engine. 2.Periodically the oil for the car must be changed, and the oil pan is drained and refilled to remove the older oil, which has lost viscosity and picked up impurities. 3.Piston is a cylindrical plug which is used for moving up and down the cylinder according to the position of the crankshaft in its rotation.