You may have heard that the motor oil needs to be changed every 3,000 to 5,000 miles because the oil goes bad. The oil doesn’t actually go bad. It becomes contaminated with dirt and debris. You may not necessarily have to change the oil every 3,000 to 5,000 miles. Your manufacturer's manual will tell you how often the oil will need to be changed.
You may also have been heard that the oil should be changed when the oil is dirty. However, dark oil may be a sign that the oil is working the way that it should. That is why the color of the oil may not indicate when you need to change your oil.
Contrary to popular belief, you do not need any additives to improve the performance of your engine. There is no reason to use additives.