Don't be ripped off by the rental car on gas

I picked up the rental last week, and the tank wasn't full.  Slightly below F.  I've driven enough of this model to know that you can drive 10-20  miles and it still says full.  So.... more than likely here's what happened.  Someone rented the car, and didn't replace the gas.  I don't know if the rental company charged them for the gas or not, but I doubt Hertz replaces the gas.  Why bother?  The next renter will take care of it.

Well, not me.  Why should my client pay for someone else's gas?  It was more than a little irritating.  Filling it prior and getting money back from Hertz would be pointless.  Later in the week I figured out what to do.  Nothing.  I didn't put a drop in.  I let them charge me for the mileage I drove.  The cost?  3 bucks.  Yep, 3 bucks.  It would have cost 10-12 if I filled it.  True, they charge more per gallon than I can get at the gas station, but in the end, I saved the client some money.  Let Hertz fill up their own damn car.