I was informed by the National guy at the exit that the company now charges $4.55 a gallon to refill the tank if you don't bring it back full. (They were REALLY pushing the refueling option which I think is a ripoff. I don't normally run the car to empty which is what they assume you will do!) Be sure to fill up before you return! I have a feeling that all the airport based car companies have raised thier price to this.