put about 4000 miles on the 06 cc short bed with lbz. every tank checked by the dic and hand calced as well. dic says anywhere from 17.5 to 18, actual hand calc says always a 1/2 mile per gallon better, so around 18 to 18.5. most of its miles are the wife driving it back and forth to work 40 miles round trip,so not really long enough to let it strech its legs. i have seen the truck get 21 mpg at best.havnt towed with it yet and it still isnt broke in yet(19000 miles)love the truck happy with the mpg