This just happened to me on a Louisville rental.

$61.00 fuel charge on an $11 + tax rental.

When I dropped the car off I used the express return. Mistake at that location I guess.

When I got the invoice/receipt via email I called and disputed the fuel charge and was told it would be reversed. I got an updated invoice via email the following day and it had the same fuel charge on it.

Called again and was told that the Louisville station had insisted that the car was returned empty. I asked how it could have been empty (when returned) when it had indicated full when I picked the car up and the indicated mileage driven was 124 miles on a compact car?

They indicated without a fuel receipt they could not correct the bill.

Luckily I had charged the fuel stop on my AMEX. I faxed them a copy of the charge and
they promised to refund the fuel charge and associated tax. We will see.

I've already disputed the charge with AMEX so I'm covered both ways.

Crook. All of them.