I got the ECM updates and TCM updates and oil update and running T6 oil now and my average has not changed, 25 to 27 on 2 lane roads driving 55 to 60ish, not a lot of stop and go, usually stops about every 8 to 10 miles depending on how far between towns. In town driving getting 21/23. Free way driving between 70 and 73, getting 26 to 27, 28, depends on traffic and elevation of road. . Have a 2016, 3.55 4 door, with air ride susp. Living in Arkansas, do not know if the weather or driving the type of roads Arkansas has laid out is the reason for my milage, but have seen milage very a lot between trucks when I read on posts and talking to people when on trips.