Our 2000 Ford F250 has maintained 15.9 mpg since we bought it in 1999. It

is now getting 20.2 mpg. That is better than 25% increase in mpg/savings on

fuel!!! Our son's 2005 Subaru Impreza Outback Sport was getting 25 mpg, and

now he is getting 30 mpg. That is a 20% increase in mpg/savings on fuel!!!