1. Properly inflated tires
2. Running the recommended octane
3. Keep RPMs under 2500 at all times
4. Keep the cruise on at 60-65 on the highway, not 70+
5. Clean air filter.

Those five things will get you much better milage, more than any mod you can do.

 

Keeping the the tires inflated to the recomended psi is the best way to save on fuel.

 

Doing the things 94rt10ohiosaid will help the current issue. If you are looking to buy him mod that could improve gas mileage (beware of the lead foot to bad mileage ratio). I would suggest a CAI (appears aftermarket CAI's with K&N filters are best bang for the buck) as well as a cat back exhaust (almost anything except flowmaster for mileage gains). And a superchips tuner.

 

Everything Ohio said is about the best you can do. Might also try filling tank all the way up (no top offs) ans do it at the crack of dawn. Also when you know you have to stop, let off the gas and coast in. Believe it or not this saves also.

 

One of the things I have been looking into for buying new tires for my truck is the rolling resistance... some tires have more rolling resistance, thus reducing the MPG. Otherwise, anything you do is all marginal in the gains and the biggest factor in MPG is the driver. I don't know too much on this, but you can buy a vaccum gauge, and install it where you can view the gauge... the longer you spend with the guage in high vaccum, the better your fuel economy is. Kind of a teaching tool.