It will make a difference...........if he changes it to a $2/gal tax. Then prices will be more in line with Europe's, and perhaps diesel won't look so shabby after all.

Americans need a drastic increase that occurs quickly to realise the differencen and make a noticeable decrease in consumption. Raising it slowly and little-by-little won't make people think "Wow, now that gas is suddenly a huge chunk of my paycheck, perhaps I should ditch the car on my way to work." I know it sounds like a terrible idea, but that's really the simpliest way to cut consumption.

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2014 Mazda 3 GT: Ø Consumption: (click for details)