Credit card transaction fees: Just like any other business, car dealers must pay a credit card processing fee of anywhere between 1.5% to 3.5% of the amount charged. If you're able to secure traditional financing with a good APR and you don't plan on paying the balance in full if you put it on your credit card, the rewards you'll earn probably won't be enough to justify using your credit card. Even if you don't end up buying a car with a credit card, you could always make car payments with a credit card to earn rewards, if there aren't fees for doing so.