To understand why we need to change our Oil, it’s important to understand exactly what your engine oil does. Your Automobile Engine has many moving Parts. These moving Parts create a lot of Friction which causes excessive Heat. Your Engine Oil Lubricates the Engine's Moving Parts while absorbing the heat emitted. This allows the internal moving Parts of your Vehicle's engine. Over time, your Engine Oil begins to break down and wear out. This causes the oil to become a less effective lubricant.
The design of current Engine Oil will last under normal driving conditions 3,000 to 5,000 miles. This is conditional on your driving Style and Conditions. All Manufacturers have their recommended service intervals printed in your owner's Manual. If you use a premium Synthetic Oil you may be able to extend your mileage between Oil Changes to up to 10,000 Miles.
As a general rule of thumb, many mechanics will recommend that you change your oil every 3,000 miles. Automobile manufacturers might suggest a longer interval, such as 5,000 miles. If you use Premium synthetic oil you may even be able to go 10,000 miles between oil changes.
So to go over your Oil Change Interval period you will shorten your Vehicle's Engine Life. If you go far enough past when your oil change is Due. Your entire engine may lock up. At that point you will need a New Engine. This can Get Very Costly.