Ever done 80% load with 2400 rpm shifts? It's not bad mileage wise but...
You'll see a lot of people gunning it off the line because they will think you are trying to drag race. It's seriously hauling tail for typical traffic.
When most people shift that high on the V6, they're accelerating in the 60-65% range, which in mileage terms is the second worst place to be next to all out balls to the wall.
Bottom line, you only need 40 to 50 horsepower to accelerate normally. If you keep the load up to where the engine is efficient and shift at 2400 you're looking at 100+ horses easy. Remember this engine exceeds the 4 cylinder's peak power levels at just over 3000 rpm at WOT.
Besides, in an engine, friction goes up roughly at the square of speed. That means going from 1700 to 2400 doubles your friction to overcome, and friction is the name of the game in mileage.