Changing your engine oil and oil filter will cost you anywhere from $30 to $75, depending on what kind of oil and filter your engine uses. If you don’t change your oil regularly, water can get into the oil and wear your engine down. This can result in excessive fuel use, less engine power, and even total motor failure. Some experts change their oil twice a year, once in the fall and once in the summer, in case moisture has managed to get in during the colder months. Neglecting these regular oil changes could cost you $500 in lost fuel or up to $20,000 if your engine ends up wearing out.