Going from point A to point B uses less energy. Please remember, i am only here for the holidays so try not to direct comments towards me personally.
Sorry, it was not intended to be an ad hominem. All I know is that a lot of political types over here advocate high green taxes for anything, but do not want to give up their comfortable tax-funded limousines. If that’s not the case for you, all the better. 
The only things i can think of is less total pollution and less overall energy used (at the hands of higher prices).
Here’s the deal. You don’t need more than two or three rooms to live well, and you can even enjoy yourself in just one room. Still, a lot of people decide to put their resources into large and ample homes because a lot of living space means more than, say, a big bank account to them. It’s subjective valuation.
By the same token, a Smart will get you from A to B very efficiently. Still, you sort of feel like a sardine in a tin can (at least some people do). Some people might want to drive the GMC Envoy or the BMW X6. They value these higher than, say, a large garden or a business expansion.
Environmentalists then step in and say, “But it’s not necessary!”. Yes, it’s the choice that a society with a high degree of technization and division of labor offers you. But if you think that car driving should be taxed into oblivion to make sure that people only drive the most economical vehicles available, you have no excuse to stop just there. You must continue to tax and regulate housing, holiday travel, free trade (just think of all those emissions that are caused by international transport !) and in the end, even silly little stuff like patio heaters (the EU has been discussing a ban on these lately) or gas cookers.
That’s why I would object, even if you can meet some politically motivated goal with it.
When energy prices hit record highs this past summer, conservation was ushered. Otherwise, the Prius and other cars would not have been in back order. There was a great piece in the London Financial Times about oil and the sustainability of its alternatives at different price levels per barrel.
Well, sure. The price mechanism is a great tool to evaluate present and future uses of certain resources. That’s why we don’t actually need government to tell us what to dig out and what to leave in the earth.
If a tax forced fuel to stay over $5 per gallon instantly, the cost of goods would increase shifting aggregate demand to the right creating an inflationary gap. I do believe that is how Keynesian’s view demand pull, or do i have it backwards?
I’m afraid I can’t answer that one, sorry.