Just bought a 2014 Silverado Z-71 4x4, Has 20" wheels with TOYO AT II tires, no leveling kit, 3:42 rear. Just made a 220 mile trip from East Texas to Austin with many small towns in between so i had many red lights with stop and go.

Truck got 18.75 mpg at the pump, not on the computer. Driving the truck with the cruise set on 68 most of the time. This truck has 700 miles on it after the trip so it is new. Sticker says 22 highway mpg, I don't think it will ever get 22 mpg at 70 mph.

I came from a 12 Duramax Z71 4x4 so comparing power would not be fair. Yes the Duramax would get 19-20 on the highway if there was no regeneration of the DPF figured in, with regen the mileage would drop to 17.5 on the hwy. When I factored in the cost of diesel, diesel piss, higher oil change cost, higher fuel filter cost it just didn't make sense to run up and down the highway and pull the boat on weekends with it. Not to mention the payment on my truck went down $200

I love the look of the new truck, it is quiet as hell, rides better than most cars and pulls my Z520 pretty good. Time will tell on the fuel mileage. I haven't made a long trip with the boat yet to see what mpg's are.

I would suspect that changing to taller tires/leveling kit will affect the mpg's as the aerodynamics are changed. The MPG's listed on just about any vehicle today are tested by the EPA and they are not driving at the typical highway speeds 70-80 that we normally drive at so I would not plan on getting actual mpg's stated on window sticker.

Maybe she will loosen up and get a little better when she gets broken in.

I haven't pulled anything with mine yet but I have been getting 20.5 mpg highway empty. Its 4x4 with factory 22" wheels so I thought that was pretty good.