I just bought an 04 f-350 with a 6.0l and I'm getting about 12 mpg. It's bone stock. I was told before that I might be able to get 17-19 mpg with a few mods. Edge juice, exhaust, and air charger. Just wondering if it's actually true. A deisel mechanic told me I could expect maybe two. Trying to justify $1500+.

 

Listen to the diesel mechanic. 18-19 is easy to do on the highway is that what they mean? around town driving is going to kill MPG on any vehicle. If I had to pick I would get

-FICM tune from PHP, assuming your is still good ($150)
-Depending on how far you want to go, SCT with custom tunes ($350)
-Some kind of monitor Scangauge,edge insight, sct livewire, etc ($150-$400)
-MBRP straight pipe exhuast ($275)
-Stock intake is very efficient already

FICM tune is going to be the best if you are not wanting to mod your truck a whole lot