Originally Posted by NadirPoint

My '07 (2500) runs a Smarty Jr. with 35" tires, 3" lift, 3.73 gear, Water/Meth with a CMGS controller, PSM intake mod and an Aeoturbine muffler for exhaust. Those are the things that might affect fuel consumption. I run the Smarty on the middle or towing 70hp setting for now, until I get the trans upgraded. It averages 18mpg in mixed driving running around unloaded or just passengers, which is what I use it for almost exclusively except for the occasional load of whatever from Home Depot.

I figure the mods are basically a wash as far as MPG is concerned. All else being equal, bigger tires with that gear and a little lift will result in poorer fuel mileage. What I've done just maintained it near a stock mileage level with that tire/gear/lift combo. It gets up to 21mpg straight highway unloaded in this trim. With a shift kit and the water/meth I expect it to be EGT/tranny safe on the max Smarty Jr. setting.