The gasoline itself wont ignite, as its not the liquid that is flammable, but rather the fumes. In that case, throwing a match in a closed container will most likely ignite the fuel, because of a build up of fumes. Which is why they have all those warning signs around fuel pumps. Replicating this in the game engine is probably not too easy, but it can be taken logically, as in a bucket of fuel being much harder to light then say a metal container that has a lid; maybe a recently spilled container being ignited much easier