Stanley is said to have siphoned the gas out of the 1968 GTO Jake was driving while it was at the gas station. Since he was handcuffed to a pipe on the side of the car and the GTO's gas filler is behind the rear license plate, he would not have been able to reach the tank to put a hose in it.
The GTO was out of gas when it was abandoned by Jake, yet when he recovers it on the tow truck, it now has gas in it.