Heck, at half of the gas stations I use, the receipt printer isn't working. To me, it sounds like another scam for rental agencies to jam customers up for bogus fuel charges. Let's face it: this is 1% about people freeloading fuel on short rentals and 99% about the agency getting up in your face at return-time.

If they tried to put this charge on my credit card, I'd simply tell them that my next phone call will be to Amex to dispute that part of the charge.