I've only tracked 4 tanks with fuelly, and 1 was driven by my wife for a week (11mpg)

I don't know how she does it, I beat on it and drove it to work for a week and got 13.4 and my commute is 1.5 miles each way (horrible for gas mileage in anything)

On all freeway, I got 17mpg with it the only time I tracked it in this app, which is typical for what I've seen for the 5 years I've owned the truck.