I understand that you are asking about the best way to store gas. And I agree with martinfocazio that you should only use rated storage containers.

However, I think that the risk/benefit ratio of the concept is undesirable.

I think a wiser course would be to consider hypermiling (change your driving) and make some vehicle mods as shown on ecomodder.com (change your car's gas mileage). Some things you can do once and save from again and again. I'm starting down that path myself, with my V8 Chevy.

If you had said that you wanted to store gas for a long time as part of a survival or bugging in plan then thats a different story, but, thats not what you were asking about.