Last month we spent 15 days on the road in
"The Beast". Put on 5,000 miles and averaged 24 mpg for the trip.
I have to admit that when on the flat land we were cruising with the key off (unless some extra boost was needed for passing on a two lane road
) but when in the mountains the key was always on. Most of the flat land running also included having the A/C on as outside temps were often in the triple digit range.
There were a few days of "spirited" driving that impacted the daily averages. Best tank was 27+ mpg and the worst was 19+ mpg. So IMO the KOTH lived up to its window sticker claim of 25 mpg/highway.