I rented from the Avis ORD location. Great, friendly staff, but when I returned the car from a 3-day rental I returned the Ford Focus at 3/4 full gas. I was charged $93.75 for 13 gallons @ $7-ish/gallon, which is absolutely insane considering I had filled the tank up twice during my 3 days of rental. How could 1/4 of a Focus tank be 13.* gallons? I called to dispute and the best they could do is to charge me for the pre-pay option, which came out to around $33. Is there something I need to know about for future reference? Despite the over-billing that occured, the Avis customer service at the ORD location was great.