The things that kill your mpg are the "leveling" lifts - I think these are the worst offender of all. Then the roof racks next and extra weight after that. I have about a 2-2.5" lift with factory rake and no roof rack. At 75mph I can still get about 19mpg calculated on the dash with 33" tires. Fully loaded with the fridge, camping gear, etc and roof rack with awning I averaged 16.7 on the dash over 1,400 miles on my last long road trip. That was with 34" E rated tires.
I really think it's changing the factory rake that causes the most MPG loss along with other stuff hung on the outside. That's why the TRD Pro also gets dinged by 1mpg is my bet. It's why I did the air suspension originally on mine and why I've been looking since then for a solution up front so I can run full air ride that I can setup to ride at least stock height or ideally 1 or 2 inches below that on the highway and then bump up to +3 for the trail.
THIS
Someone, maybe one of the engineeeeeers here, wrote a thread on fuel economy. I would link it if I could. But the basics are:
1) Math -- did you do the math to confirm what mpg you're getting?
2) Route and conditions -- obviously stop and go commuter driving gets poor fuel economy
3) Driving habits -- slow down maybe?
4) Wheels and tires -- without plunging into sprung and unsprung mass formulas that I can't complete, lighter wheels and tires produce better results; also, tire pressure
5) Weight -- not just your weight, your rig's weight, but watch your figure too
6) Suspension -- If you're not putting power to pavement, but it's getting soaked up by your suspension, that's bad; also, center of gravity, but it probably rolls into suspension
7) Aerodynamics -- we didn't have a good starting point, and most of us are making it worse
Is there more? Probably
and these!
I have clocked my mileage every tank with the CarXpenses app since I bought the truck six years ago.
I have a 2.5/2.0 (leveled), extra weight (AL armor, battery, air, winch, fridge, rec-gear, passanger + dogs

), and had BFG KO's C-rated 265/70r17's for years until I wore them out. I'v averaged 15.6 mpg. Highway only trips I get 17-19. City I get 11-16. Offroad+highway same as City.
I just "upgraded" to D rated Goodyear MT/R's 285/70r17 I have put in four tanks so far:
14.08 - city
12.59 - city + offroad + return highway
15.27 - city + highway
10.98 - offroad + return highway
So time will tell. I picked MT/R's specifically because they are D-Rated and NOT E-rated tires. C's I think are okay but this platform feels like it needs just a little more when you build it, even mildly, and E's are just overkill for general offroad and regular usage.
I too do think that going nose up really borks your mileage the most, second racks and crap on them. We are driving bricks, not as boxed as and FJ or even a Jeep K-series (which incidently get worse mileage than us) but bricks none-the-less
What do you expect if you want to go where you want and look cool doing it

:twitch: