Just some observations so far:
I've tried 93/92/89/87 octane and don't see any change in useage or performance in my 2006.
Before I tow the boat I usually let the tank get as low as I can for a few days and fill up the rest of the way with 93oct.
I have been getting between 21.8-22.6 mpg on the highway.
Around town 15-16.
Towing a 22' boat (4000-4500lbs) I get 11.4-11.6 on the highway at 65-70mph and 13-14 on back roads (I guess wind drag at the higher speeds??).
This is on a '06 4x4 S with the General Grabber tires. 2,850 miles driven so far.