Nothing inside your car is renewable, so it will eventually either run out or get old and cease working to its full potential. Both can happen with your oil, but if you get to the point where there is no oil left, you’ve probably done some serious damage to the engine already. Oil is an essential lubricant for your engine. It creates a buffer between metal against metal , such as the pistons moving in the chambers.
Substances like dust, metallic shavings, and even antifreeze contaminate motor oil. Even the additive package that is part of fully formulated oil will eventually break down and become a contaminant. As all of this stuff gets blended together in the oil, a sledge-like substance is formed. Many mechanics actually refer to it as engine sludge. This stuff is sticky and starts to inhibit movement in the engine, which is exactly the opposite of what oil should do. The filter will remove dirt and contaminants for a while but it will eventually clog, too. Once that happens, all that stuff will bypass the filter through a relief valve.
So What Does Oil Actually Do?
Quite simply, it lubricates. Inside your car’s engine, metal parts are constantly sliding across each other at extremely high speeds. The friction of metal against metal at that speed could generate enough heat to destroy the engine — if there isn’t quality oil to lubricate the metal parts and help them slide more easily.
Oil is a long chain molecule. The long molecules of oil work their way between the metal parts so that moving metal parts never really touch each other. But those long chains don’t last forever.
Heat and the motion of the engine break down the long chains into shorter chains and those chains are broken down even more. Old oil is better than no oil and will at least keep the engine from seizing up. But as the molecule chains get shorter, the metal parts are more likely to come in contact with each other causing more wear inside your engine.
This is why you need to keep your oil changes as close to schedule as possible. New oil always works better than old oil. It won’t kill your car if you go over by a few hundred miles, but letting it go too long will start to damage your engine.