Thanks for the links. I searched but didn't find them.

I am not a lawyer, so I don't know specific terms and cases. However, from a few contract law courses I took this does not seem legal, because the duty to fill the tank exactly at the pre-determined mark is impossible to fulfill unless the customer is willing to pay more to be on the safe side. Everyone understands and can perform the duty to fill the tank to full, but you can't expect everyone to be able to figure out the gas mileage of an unfamiliar car and skillful enough to make the gas gun stop at the precise moment. This term will be nullified if it appear in any court of contract law.

I guess nobody cares for the couple of extra gallons when it's cheap, but with today's gas price, it amounts to two or three level grade, or half day rental rate.

I never use Enterprise for my own leisure rental, but what they do is simply unethical business practice, if not illegal.