Many years ago I had a 1-day rental (~12 hours) in SF. Picked up in downtown SF and while driving around San Jose, some light on the dashboard came on. Could not tell what the icon meant and no owner's manual. Called Avis and they told me to exchange it at a location a few miles away. Went there, they gave me a new car, but the key would not work with it. Finally, a 3rd car was given to me and we were back on our way.

Later that evening I was running late to SFO and did not find a gas station on the way to the airport. When I was returning the car, the rep asked if I filled the car and I said no. He then presented me with a receipt with an outrageous gas charge (it calculated the miles driven on the 1st and 3rd car and based the gas charge on both). I complained and he told me that I would have to talk to someone inside. Went inside, explained how this was my 3rd car in 1 day and that it cost me time to do all the swaps, and the inside agent reversed the gas charge immediately before I finished my story.

As others indicated, a gas charge on a broken vehicle is ridiculous, but you do have to say something to them as they will not necessarily waive it automatically.

BillJ