We don't need any of this. I wish to keep this thread open, so get back to the topic.
A friend of mine came up with a pretty good idea.
At a gas station, how about weighing your car to determine the gas price? Generally, I would think that fuel efficiency would correlate pretty well to the weight of your car, since a complete discretion of models would be cumbersome for the gov't. So then all the people who drive heavy vehicles like the Hummer would be discouraged to drive them regularly.
Not only that, gas stations should be designated into two types: one for filling up cars and one for filling up anything. The ones for filling up cars can give you a relatively cheaper price provided you drive a 4-cyl. compact, but also prohibit filling an exterior container (this is a possible loophole). And the ones where you can fill up anything sell gas for a fixed but high price (like you automatically had a 5000Ib vehicle).