I wouldn't know much about a half ton truck, but my 2015 5.7 Hemi 4x4 is lucky to get 17 mpg going 55 with a tail wind. The difference in the horsepower, torque, and weight has a lot to do with it, but I still don't know a single person who drives 55 and gets 19 and up mpg with a 3/4 ton truck, and don't know anyone who brags about mileage in the half ton except for Moparts...