Gasoline wont break down the plastic that the oil tank is made of? I know only certain kind of poly carbonates can stand up to gasoline. I would just be nervous that it would break down and mix with the fuel and do alot of internal damage to pretty much every piece of the engine. Great idea though i would love to have an extra half gallon. especially after i hit my reserve and im like ehh it'll be good for a little longer than i forget and its like wahhhh.....brppp.. uh oh?? I wonder how to find out the type of pc the tank is made and check to see what reacts with it?