I have 2017 Sport that has leveling kit and 33s. I drove 70 mph a few months ago on flat interstate (about 500 miles round trip). Made 21 mpg. Weather was nicer in the 60s for that trip. Most of the time all around town is 17 or 18. Seems that MPG goes down in winter cold days overall. I use 87 ethanol mix here in South Dakota. I also installed a converter box cable behind instrument cluster to compensate for larger tires, and computer seems to read correct speed and mileage now. I’ve checked mileage with pen and paper also and seems to be the same. When I bought truck, I assumed 18-20 would be the norm. If I removed leveling and went back to stock, would not be as fun to drive.