I brought a new motorbike on my Amex once and charged the £8,000 to my Amex. The dealer took the card without question.

The dealer probably paid a merchant fee of 4% (£320) of the charge to Amex. I got the reward points, but given the option I would have taken a discount off the price and paid cash. Even half the merchant fee would have been more valuable than the points I got.

If a dealer is willing to accept any credit or charge card for a large transaction like this then it is worth mentioning the merchant fee and asking if they will give a discount for payment by another method. Even if you get 2 or 3% off the price, the discount you get would more than compensate you for the miles you miss out on.