Good points all - Blue Horse, Farm Boy, and Al.

I've done many of the items these three gentlemen have suggested. I'm adding more gradually, as time and weather allow. In fuel economy circles we've found there's no single magic bullet, but a combination of techniques and modifications can get you 25% - 35% more than EPA and sometimes higher.

gassavers.org
ecomodder.com

I'm currently getting roughly 26.5 mph, auto tranny, wagon, no roof rack. Mostly highway, in approx. 45 degree weather, still on winter-mix fuel. That's a 60 mile commute with several miles of city driving at one end. Last summer I was getting 30-31 mpg on a similar 60 mi. commute; I expect to be up there or better again this summer. Warmer weather and summer fuel mix always help.

Why does the air dam work? It helps reduce the amount of air getting under the car. As the underside isn't particularly aerodynamic, the less air down there the better. Many modern makes are paying a lot of attention to smoothing out the underside. Lexus, BMW, Lotus (Elise), and Honda and Toyota on their hybrid cars.

An air dam works best when combined with side skirts to improve the reduction of the amount of underbody air. Also a flat underbody covering is a really good thing. A partial grill block (winter use only for some cars) also reduces the amount of air banging around under the car.

I have to say my car has become much quieter after the various mods I've done. Electric radiator fan got rid of the constantly spinning radiator clutch fan and its noise. Aero mods are reducing the amount of air whoosh around and under the car.

Power needed to overcome air drag goes up with the CUBE of the change in speed. Any reduction in drag is a good thing for a guy with a 60 mile commute.

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Sven: '89 245 NA, 951 ECU, expanded air dam, forward belly pan reaches oem belly pan, airbox heater upgraded, E-fan, 205/65-15 at 50 psi, IPD sways, no a/c-p/s belt, E-Codes, amber front corner reflectors, aero front face, quad horns, tach, small clock.