Make your best deal with us on a new automobile and we ' ll change your oil free for as long as you own the car " . If you purchase a car from this dealership , you expect to have four free oil changes per year during the five years you keep the car . Each oil change would normally cost you $ 30 . If you save your money in a mutual fund earning 2 % per quarter , how much are the oil changes worth to you at the same time you buy the car ?