The arithmetic doesn't seem right. I tried 2 gallons a day for a user who commutes to work, for 20 days a month. Thats 480 gallons tack on 1.5 times that for leisure driving and out of town trips and yoy have 720 gallons. If the mpg is up from 25 to 50 then you save the cost of 360 gallons. At $4.00 a gallon this is $1440 for savings per year. At this date June 2007 the price of gasoline at the pumps is $3.75, so $4 is not unreasonable. And improving mpg from 25 to 50 is not unrealistic if you include improvements that should occur if car companies continue to develop this technology. At $1440 you would recover the cost in over 2 years. And its a smart bet for car drivers and car companies, and a smart bet for the US and the global economy to keep gasoline prices in check as China, India, Brazi,l and Russia, and the rest of Asia and the world increase their oil consumption.