User: Why should I change my car oil?
Assistant: Changing your car's engine oil is important for the engine's performance and longevity. The oil plays a critical role in engine operation, by providing lubrication between metal surfaces. Without oil, these surfaces will rub against one another and cause permanent damage and unrecoverable damage to the engine. Always use the engine oil type that is suggested by your car's manufacturer, and change the oil at the suggested interval. For many modern cars, this is either every 12 months or after 5000 to 10000 miles, whichever come first.