15,000 miles worth of MPG
For what it is worth, this weekend I hit 15k miles on my truck. When I picked my truck up it had 3.8 miles on it so I reset the Trip B trip meter to 0 and have not reset it since.
I have averaged 13.8 mph for 15,000 miles. About 6,000 miles are highway at an average speed of 80 mph, maybe 500ish miles offroad and the rest in town on residential streets. Note that the trip meter does not show the 10,000 place.
I have used 91 octane for all but the first couple of tanks of gas. In town I run the economy tune from 5 Star.
As a side note, if you take the 15,000 miles divided by the 429 hours driven you get an average speed of 35 miles an hour. Driving around town to and from work I probably average right at 35 mph (never get on a highway) and I consistantly get 13.8 mpg on a tank of fuel, right in line with my 15k average.