ive been tracking my milage intensely over the last 2 months with 90% highway driving in the extreme cold and Ive been managing about 17-20 mpg. I normally can reach about 240-270 miles on a 13-15 gallon fill up. This is using the same gas station and alternating between two pumps. This is with 33's and 4.10's Ive been able to hit the 19-20 mpg range by keeping my rpms under 2000 and trying to keep OD on as much as possible and trying to prevent shifting on hills.
I drive 240 miles every two days so filling up is so easy, fill up at the same station on my work drive every other day. Id say i get 240 miles from the Full mark to the 1/4 mark on a regular basis.