Don't believe the hype, Redflare. There's really not much you can do mechanically to improve your vehicle's gas mileage besides keeping it properly maintained. Personally, the single thing I have noticed that makes a big difference in my own gas mileage is to drive smoothly and without hard acceleration. The difference in your gas bill at the end of a week of driving aggressively and driving smoothly is substantial.

I see it all the time--I'm cruising down the street and a car pulls up close behind me, changes lanes to accelerate around me...and a minute later, I catch up to the guy stopped at a red light. As soon as the light turns green, they zoom away again. So many people drive that way, and they complain about the price of fuel?