Car engine oil plays a crucial role in the health of your engine. It lubricates internal parts to prevent them from wearing out, it cleans debris and prevents them from causing damage and it cools the engine by transferring heat from work parts. Just as important as quantity is the age and quality of the engine oil. As the oil ages, it gets thicker and the more it becomes the less efficient it is and then it can also damage your engine rather than protecting it. The frequency with which you should change the oil depends on a variety of factors such as the age of your vehicle, the type of oil and your driving habits and conditions.