What Does Engine Oil Do?

The picture shows that sometimes we need friction so we don't go sliding out of control. One place where we do not want friction is in our engines. Engine oil is there to lubricate the metal surfaces and get rid of friction. In a properly working engine, a thin layer of oil separates all metal parts so that there is no metal-metal contact. Instead we find metal-oil-metal contacts. But reduce friction is not all that oil does.

Oil also helps to cool the engine. There are places where the water cooling system just can't reach, like down in the crankcase. Oil gets in these areas and removes the heat. Another role of oil is to help the piston ring seal the combustion chamber or head off from the crankcase. Oil also scavenges tiny metal particles which are worn off when engine surfaces work against each other. These particles are then removed from the oil by the oil filter. Acids can be formed by chemical processes occurring in the combustion of fuel. All gasoline has at least a small amount of sulfur in it. This sulfur can react with water (brought in with the air) to produce sulfuric acid. The sulfuric acid is dissolved in the oil, which has acid neutralizers in it.