Both mileage and time will degrade oil and compromise how effective it is in protecting your engine. In either case, regularly checking your oil is the best way to determine if it’s time for an oil change. Check to see how much oil you have in your car and whether it contains any gritty particles.
Beyond the oil level and its appearance, you should check your owner’s manual for the manufacturer’s recommended oil change service schedule. This may be every three, six, or 12 months. If you go by oil life, keep in mind that even if you don’t put many miles on your car, oil is still degrading over time and should be changed in accordance with your vehicle’s recommendation.
Mileage-based oil change recommendations are usually in the range of 3,000 miles for older vehicles. Late-model cars and trucks can go much longer—anywhere from 5,000 to 7,000 miles for most vehicles.
In any case, new, clean oil is essential for keeping your engine clear and protecting it from breaking down.