I know this is heresy around here, but keep in mind that trying to use a credit card will hurt your negotiating position. Mercants pay something around 2-3% of the amount in processing fees to the credit card company, so to them it's like giving you another $600-$900 off on the price of a $30,000 car.

Technically they're not allowed to charge extra for CC or discount cash payment, but good luck arguing that. Those rules are in their contracts with the Credit Card companies.

The heresy I refer to is the thought that the points you get might not be worth the increased cost of your car.

MYMMV