Reply #12: There has been a retrofit kit invented to increase mileage on existing cars

[meow2u3]

It's call the HAFC-PICC, or hydroassist fuel cell with preignition catalytic converter, already on the market. I saw the ad in US News and World Report, and according to the manufacturer, it's guaranteed to get you at least 50% better fuel economy. This is a solution for the here and now, and it costs a few grand, as opposed to a 6-figure price for a concept car.

http://www.preignitioncc.com/us/index.htm