I went from stock 2657017 31.8"to king ranch stock 2756520 34.1" tires.
your highway cruising mileage may go up max like 1mpg but mountains snow on the roads and towing will diminsh the gains of taller tires by placing more load on the truck. your around town mileage will also go down. i noticed a loss of power with the taller tires obviously theres enough power but there is a noticeable drop. also the wider tire will hurt mileage compared to the same height skinny tire. also being in alaska the wider tires are worse for winter driving. if you get taller tires dont forget to recalibrate your speedo or at least realize it will read slower than your actually going.