Most mods discussed on this forum are about power or noise, relatively few focus on mpg. Luckily, many of the power mods are also mpg mods, if you can manage to drive responsibly despite having great power at your command.
One contrarian idea would be the one championed by Eric.Smit; get the Trifecta tune (there are other tunes but the one most of us know well is the Trifecta one) but don't get the Select-a-tune, because oddly the "performance" tune seems to deliver better mpg than the "eco" tune. Having Performance coupled with your Cruise Control may help you keep your foot out of the bottom half of the pedal where your gas flows like water.
Another, and this one Eric will hate, is to get the Injen intake, rather than one of the real power ones. Injen markets itself as a power intake, but because of the position of its tubing, ends up drawing warm air, which means it improves mpg rather than power despite allowing more air flow like all the intake mods. They lie, but the lie may work in your favor if you can stomach it.
Third, increase the pressure in your tires, but here's the thing; this mod,while incredibly cheap and fairly effective, is a bad idea in slippery weather. If your winter is anything like the one we're having here in PA, leave this alone for a couple more months. Or on a dry day you could inflate them, and just remember to deflate back down to normal pressure before driving if you get bad weather again.
Fourth, move somewhere warmer. The cold winter air is going to make a mockery of any of your efforts, my best MPG has gone down as much as 10 due almost entirely to colder air, it is pretty amazing (and why I suspect the Injen may be in your future)
Fifth get a gauge of some kind. Ultragauge works very well and is very simple, but it becomes less useful as you mod your car more heavily. But at any rate, something that shows your current instant and "short trip" (which is your mpg since you last turned the car on) mpg will really help you train yourself; driving habits are the single biggest boost or impediment to high mpg. I can get 44mpg on a tank, and drive the same road in the same weather and get 32mpg, just by driving for fun rather than for economy.
