I've been able to regularly get an additional 25 to 30 percent increase in
gas mileage by just limiting my top speed on the highway to 55mph.  I also
shut off A/C while around town, prevent long idling (I shut off while at the
ATM, etc), and use cruise control as often as practical.   It does work, and
I'm a true believer.......

Mike B.

 >if there was a simple add-on device that
> would even yield a 3 % increase in fuel economy with >no other
> downsides...............they would offer it.
> there is no free lunch.