Originally Posted by tarheelnj

It can be frustrating to get a charge, even when you filled the tank just before leaving for the airport, particularly at those airports that don't have a gas station anywhere close to the airport (like GSO for example). Sometimes, Avis will have a flat rate for gas if you drive <75 miles. If you buy gas, be sure to keep the gas receipt and show the person at the counter (or include it in the envelope when dropping your car off after hours). You can do the math based on local gas prices whether it's worth it. Generally, you have to be pretty close to 75 miles. (My record was returning with 74 miles once.). I've disputed a gas charge after renting, and they ask for the name and location of the station where you filled up, so save that receipt (or at least a photo).

Taking photos of the odometer, fuel level, license plate, any existing damage, etc. should be standard practice for everyone.