Most recently I used my Starwood Amex to pay for a new Mazda Van. I started by contacting the dealer, informing them we were in the market and advising them we would only purchase if we could use the card.

Last year, I paid for my new Lexus in full on my Aadvantage Visa card. Prior to presenting the card, I had obtained a letter from Visa International stating that refusal to accept a Visa card by a merchant is a contravention of their agreement. Although most attempt to, a merchant cannot limit acceptance of the card. You either accept it or you dont. When in doubt they should read their agreement with Visa/Mastercard.