With these newer 6.7's with the emissions you will not see the best of miles per gallon. There are claims of guys getting 20 miles to the gallon with these trucks, but these claims are not true. You want better mileage, and air-flow delete the emissions, and get a tuner so the truck will not go into limp mode.Other wise you will just have to live with fact that emissions are part of your truck, and you'll have to deal with that aspect. There are a few tips to achieve a little better miles per gallon. Check your air filter, fuel filter, proper tire pressure, a high lift kit with bigger tires also affects mileage. There is a product called Power Service Diesel Kleen, it lubricates the entire fuel system, cleans dirty injectors, less down shifting, higjer cetane boost, protects pumps, faster cold starts, and also prevents injector sticking. Use it at every fill, I mean every fill up to get the benefits. Hand calculation is way more accurate set up versus reading off of your truck readings.