Car Engine and Other Systems - Avoid overfilling your crankcase with oil
Don't overfill your engine crankcase with oil. If you do, the oil can rise into the crankshaft, where air bubbles will get churned into the oil.Your oil pump can't do a good job of circulating oil with air bubbles. The result can be overheating and stress on engine components. Overfilling can also foul your sparkplugs. In fact, overfilling is a bad idea with all automotive fluids.