Ok mileage figures just in.......I really care more about comfort and utility and don't give a crap about gas mileage or I wouldn't have bought Avys. My normal gas mileage of 16-17 mpg in mixed small town mountain driving is just fiine.
That being said I had a chance to play with it a bit because I took three identical round trips from Harpers Ferry to Gettysburg over the past months, 2012 Avy, Shell regular gas (same tank of gas round trip), flat ground for a change, all highway non stop driving at the posted speed limits of 65 and 55, 6 spd, 20" wheels, 2:42 rear end, fresh Mobil 1, 8.9K on odometer
Trip with AFM active..........22.1 mpg and 21.7 return
Trip using Range module.......20.8 mpg and 20.1 return
Trip using Range module and a Weathertech deflector over the closed sunroof............21.9 mpg going and 21.6 return
It appears that under ideal condtions the AFM may actually save a miniscule amount of gas when active, but not as much as you could get by removing the roof rack crossbars or using a sunroof deflector. I figure that the deflector must reduce the wind resistance of the rack cross rails.
The Range module worked perfectly by keeping in V8 and vehicle reverted to AFM operation as soon as removed. Worked fine in the '12 and the '13 but I don't plan on running it full time just yet. Waiting to see if the post '11s updated engines with the valve cover/PCV, AFM discharge valve baffle, and redesigned valve lifters mods have fixed the high mmileage oil burning problem, especially since GM continues to use AFM technology in the 2014 V8/4 and V6/4 engines.