Your lucky with 17mpg, but I guess thats due to the diesel. I'm getting around 17mpg right now only stock tires. But I've already got a 3" body lift on, 2" add a leaf, Ford Keys cranked to level it out and a shackle flip on my 2005 sierra. I currently have a 6" Superlift full drop lift sitting in my garage waiting for it to be nice enough for me to install, along with some 39.5"x13.5 Iroks to go along with the whole setup. Spent wayyy to much and I still need to regear. The upsides to driving around a lifted truck is the attention you get, and theres really nothing more fun to have on and off road. Don't bad mouth it until you've drivin one.