I'm going to Australia in December and will be renting a car on a couple of occasions. So far, it's looking like Hertz with the AmEx Platinum CDP is giving me the best deals. (Tried a AAA CDP since there are lots of reports of it being cheaper, but it's not on the ones I tried.) The question I have is if there will be any issue if I pay for the rental (from reservation onward) with a Visa card but am using the AmEx CDP. AmEx's CDW doesn't cover rentals in Australia, while Visa does, hence the motivation. I'll have my AmEx Platinum on me if they want proof that I've got the card, but I don't want to have any hassles.