When I was at the Wixom assembly plant (Lincoln LS, Town Car, T-Bird) they said they would like to completely fill the tank, but they can't. I was told by my guide that the amount of gas put into every model car was carefully chosen. They put in as much gas as possible without causing any problems when the cars are tilted at the extreme angles they go through when loading and unloading them on the trucks and trains. The gas pump on the assembly line automatically meters out the proper amount of gas for each vehicle. It has 3 different amounts since there are 3 different cars running down the line.