I don't know about using gasoline since it's so explosive but a solvent of some kind should work. The kerosene idea might work. You can try a radiator shop to boil it out IF you can find one that will do it. Radiator shops around here won't touch old gas tanks. As a last resort if nothing else works you can acid clean it then coat it inside. If you do that be sure to follow the instructions exactly. If you don't the coating can fail. I've been pretty successful using coatings but some here haven't. Good luck.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.