K and N air filter. Bully Dog Triple Threat set to tow/economy.

19-23 general driving no load.
11-13 towing 10k boat to the keys with the truck loaded down as well.

04.5 Quad Cab stock wheels and tires.

Driving 55 with no load, computer registers 26 mpg
driving 60 with no load, computer registers 23 mpg
70 = 21
75 =20

 

I think I'd try something to add some timing. If you're worried about the warranty, a Smarty is supposed to be undetectable after returning to stock. A modded air filter box will let it pump more air, as would a Quadzilla boost fooler. All of those items together should net you a considerable mileage improvement as long as you run the Smarty on level 1 and stay out of the throttle. (Good luck with that!)

 

18mpg highway
10-11.5 pulling 11k toyhauler 70mph

 

21-22 empty highway 65-70 mph running 1800rpm

19 around town

13-14 towing worst 11.5 up through nevada in a headwind with high trailer

03' ho 305/555, CC 4X4 LONG BED, smarty LEVEL #5, 4", AFE