Car rental companies are coming up with a new way to fee you to death over gasoline.
Avis is using a new technology that can read the amount of gas in the tank down to tenths of a gallon. If you return it just a hair less than full, they will charge you at just under a dollar per tenth of a gallon of gasoline. That's the equivalent of almost $10 a gallon, when you factor out the numbers they're using!
And they're not alone. The Washington Post reports Hertz is going to a similar system, but theirs will also be able to shut down your rental by remote if they're unhappy with you for some reason! On the plus side, they will be able to unlock the car for you remotely should you lock your keys inside.
But the idea of electronic fuel monitoring is a nitpicky kind of thing. You never want to accept the rip-off fuel options that the company offers you. What I recommend is that when you do fill up before you return it, you should do what environmentalists don't want you to do: Top off your tank.
That's the only way I know for sure they're not going to rip you off. So be warned that this is the next area they'll try to bleed your wallet. You need to be prepared!