When we bought my '05 Acura RL, they originally let us put up to $10,000 on a credit card. After that, we'd pay half of the merchant fee. After some haggling we got it up to $12500 then $16000, then finally $24,000. We were happy. We were going to pay cash anyway, so why not charge it when we'll just pay it back next month? We were denied at first, but I called up Citibank and they lifted my "per-transaction" limit.

Then, on our next car purchase, for an '05 Honda Odyssey, they had a strict limit of only $4500 on credit cards, but we got it up to $6,700. The month before we did this, my wife opened a new Discover Platinum card. She decided to charge it to that. We had no interest for 11 more months and then paid that little down payment off. So, with a little research and haggling, you could put the whole car on a 12-month 0% APR credit card and get the miles (and Blue from AMEX (not Blue Cash) gives you 0% for 15 months)!