Unfiltered oil can, over time, develop hard and harmful particles, and the last thing you want is for them to pass through an old or broken oil filter, inflicting lasting damage on your engine. It is recommend that you change your oil filter every 5,000 miles or so, but be aware that only certain filters work with certain cars - the wrong ones can cause leaks and sometimes irreversible damage - so be sure to consult your owner's manual before purchasing, or contact Euro Car Parts and allow us to help you find the product you need for your vehicle.