I think each of the mods do a little to help overall performance. My problem is I find the added performance makes driving the damn thing so much fun you end up driving it a lot harder. I have been modding hard for the last two weeks and my last fill up showed I still got 15.25 mpg and I have been data logging and basically driving like I stoled it. Great fun...

 

The best combo for mpg is a JetChip and a Tornado intake insert. You'll see 7-8 mpg easy with that combo.

 

Seriously, I've got an SC3865 tuner, CAI, LT Headers, E-Fan, a VERY free flowing exhaust, have re-geared and I get about the same 12/16 I got stock.
Although I don't bi*ch a bit, this pig is now up to about 7000# and is about 55 HP over stock...

 

Yeah, once I stop leaning on it all the time, I expect my mpg to be better than before I started (17.5). i really need to weigh the old girl , as I expect her to be relatively light for being a truck.

 

Just make it run more efficiently than it does stock. With all i got in mine and how hard i run mine i still get 16.4mpg. Up to a certain degee you want to build up the hp as much as you can so you can get up and go easier

 

With the right combo of mods you can get over 20mpg on the highway. It takes some easy driving (65mph) to keep the mpg that high, but it can be done.

 

getting twenty mpgs on the highway could prob be done with a stock truck . i haven a exhaust and a crappy intake and got around 20 with it on the highway crusin at 70 but as soon as i step into a city (where i am 95% of the time) i get a crappy 12, at the absolute best. i'm getting superchip 3865 soon though, i'll let you know what gas milage i get personally after i try it out for a week. of course it will be gas milage on the perfomance setting ,i didn't buy a chip because i was worried about gas. i want to destroy 5.4 fords.