The blog “Blueprint for Financial Prosperity”, which obviously thinks stealing should be part of your blueprint for getting ahead, claims you can use your American Express card to buy Costco’s cheaper gas, even if you don’t have a Costco membership:
All you have to do is swipe an American Express card first, when you would normally swipe your membership card, and then swipe it again for payment. Afterwards, it will let you buy the sweet sweet nectar of condensed dinosaur bones at rock bottom prices without the $50/year membership.
Since I’m a member and would never do a scam like this anyway, I don’t know if it will work. In fact, I’m posting this mostly to make sure Costco sees it and fixes the problem. In my mind, them trying to get Costco’s gas without a membership is almost like stealing from me, because my money goes to keeping Costco in business which is how the cheaper gas exists in the first place.