I believe that's only true when the substance in question has flammable vapors. I.e. gasoline, but not oil or diesel. I suppose in the latter case, it would pro

I believe that's only true when the substance in question has flammable vapors. I.e. gasoline, but not oil or diesel. I suppose in the latter case, it would probably not explode on collision whether empty or full. But if liquid leaked out in the crash, I guess it could then combust.