Got 16.9 mpg last tank! That's got to be the best I've seen in as long as I can remember and it wasn't "optimum conditions" IMO. Drove about 3 days of my regular commute which is 17 miles one way and averages a good mix of 55mph roads and some 35mph city streets with traffic. Then yesterday I shot up to Ocala to sell some parts and averaged 75-85mph on the highway for about 55 miles one way. Got there at the predetermined meeting time of 1815 and upon arrival, I got a message saying the buyer would be there more like 1900-1915. So I watching videos for an hour with the truck idling and AC on blast. So with about half of my driving being regular commute and half higher speed cruising with an hour of idling in between, I got 16.9 mpg! Before the alignment, my average was just 13.5-14.5, and highway not being a whole lot better.
A proper alignment really helps mpg and I suppose this truck's alignment probably hasn't been right since I first got it. It makes me really want to get a set of lighter wheels and put some highway tires on it to see if I can squeak closer to 20 on the highway. I'm sure there's a few things that could be cleaned up on the tune as well.