High teens from a Power Wagon?
Call me skeptical.
I mean, sure, I was able to get 18.5 MPG on my Suburban. ONCE. And that was on a 450 mile round trip on mountain roads with no stops, no traffic, and almost nothing in the truck (on the way up, nothing, on the way back a motorcycle sidecar that probably weighed 100lbs total.)
But that didn't budge the needle on the 'average' MPG of about 12.
Which is what I'm guessing a PW would get, on a good day. With stock tires, no lift and no weight in the bed.
And before someone says "I totally know someone who regularly got 25mpg on his PW" keep in mind that people lie about MPG all the time. Mostly they lie to themselves because when fuel prices spike they hate to admit they bought a gas pig.