I use enterprise regularly but this is the one thing that bugs me. It's difficult to gauge how much fuel to replace and often involves a couple of stops to turn the key to see how I'm going.

I've probably more often than not put more fuel back in, and the one time I had it slightly under I got stung with a refueling charge.

Thankfully I use the same branch every time and they kindly used the charge as a credit for my next rental.