On the site, I have a piece in which I claim that the best argument for a gas-tax hike is that it would redirect oligopoly rents from OPEC to the U.S. Treasury. One thing I did not note is that this argument is in tension with the claim that a gas-tax hike is a good idea because it would promote conservation. The anti-OPEC argument assumes that the price is already about as high as it can go, and any tax would come out of the profits. The conservation argument assumes that the price will go higher–indeed, it is more effective to the extent it leaves OPEC with the same share of the revenue from any particular gallon.