This game is the only place where I can find strategy information, so it would be better to talk about it here.
If you don't have any gasoline, check the items section of the menu (M key) and if not, you have already given gasoline to the guy.
There is nothing else to do in this stage except to get the gas.
Also, just to be sure, could you send me a screenshot of the scene where you get stuck?
I don't know if it's okay to post it or not, but it would be more helpful if you have it than if you don't.