What can be wrong!

Do a compression test the 2.7 s have a problem with heads cracking and valve seat wear even on low milage engines

 

I would do this, get a full tuneup, and make sure and get air filter replaced, that can be a huge contributing factor to poor mileage, that engine needs to breathe!

 

OP, did you try calculating again yet? What were the results?

 

God damn man in running 315/75/16 with 4.56 gearing and getting 22+

 

Just filled up today and got 244 miles to I think it was 16.xx gallons and got 15.44 mpg......

Honestly I don't know if SoCal gets winter gas or not but my trucks always had shitty gas milage I think. I used to have 5.29 gears in my axle which was making my trip meter read more than it should and i was getting 19-21 mpg and now I put back stock 4:10 and its correct for my tire size of 265/75, now since my mileage is reading correct I am getting true mpg and it's 14mpg which is garbage.

I have a k&n that I cleaned 6 monthes ago but last time I checked it it was still clean but I can clean it again.
Does spark plug gap have anything to do with it?
I have new plugs and wires.
I'm gonna also glean my maf sensor but my engine isn't running rough or oddly??