During a full-service oil change, an Auto Service Professional will: Change your vehicle's motor oil using full synthetic oil, synthetic blend, or high mileage motor oil, depending on your vehicle. Replace and recycle your cars used oil and oil filter. Oil keeps your car's engine running smoothly while reducing the wear on all its moving parts.
The most common issue is that the parts in your engine will become too hot. This can cause the engine to run less efficiently, and as time goes on, it can cause the engine components to warp and wear out. Eventually, if the oil is not changed, the entire engine will shut down and have to be replaced
Over time, that oil breaks down and becomes contaminated with dust, dirt and debris from the engine as well as the environment.