Actually, you have a limit on the number of gallons you get per year. So the more you drive, the sooner you will go back to paying $4+ for gas. And you are really just arbitraging the money - for most models, you give up more in dealer incentives to get the gas card than you would have paid for the gas in the first place. And if you don't use up the full alotment, you are SOL. So the deal only makes sense if you will use all 500 gallons/year, and gas prices stay high enough that you'll save more than you lose in incentives.

The deal is limited to 12,000 miles per year. I wonder if they determine the number of gallons based on the EPA mileage estimate or actual mileage. If it is based on the EPA estimates you would only get about 10,000 miles per year worth of gas. And there are cars that get much better gas mileage than those anyway if that is your goal.