[JeepNmpg2]

dcwhittney89 - If the muffler mod is done in conjunction with a high-flow intake, yes it may help your economy (when I did mine, I seem to recall it bumping up 2-3%), but for the cost a tonneau would be a better mod if you have a longer bed. A truck cap while it decreases the air trapped in the bed, will give you what the SUV's (including mine) have an issue with is the "bluff tail syndrome", where the back of the vehicle is flat, and it causes a lot of drag. Depending on the aero of your vehicle already, it may increase or decrease your FE.

Now don't get me wrong, I love the sound of my engine with my done up exhaust, I just didn't really do it for eco purposes originally.

Oh, and if you do decide to do the muffler, find a local shop to weld it in, usually for around $20 since it'll be pretty quick and easy for them.

Lastly, I would remind you that the first, and often best adjustment you can make is to the nut behind the wheel. Check out the 65+ driving tips, and you may find some that will help you to increase your FE without spending any cash.