I expect that with winter blend fuels coming in, the MPG's will drop a few.

As to speed, I tend to do the speed limit + 5, or go with traffic.

 

I have a Dodge Magnum with the Hemi in it that has a similar, AFM type system. I bought the car new in 2007 and it now has 82k mostly highway miles. Doesn't burn or lose a drop of oil. The oil comes out almost as clean as it went in. Chevy dropped the ball.

Besides the AFM, did you do the regular stuff like check the brakes and change the fluids (axles, trans, transfer case, antifreeze, brake fluid, power steering fluid etc)? I bought mine with 105k and have been slowly changing all the oils and fluids. Peace of mind plus you get to know your new vehicle better.

 

I'll be curious to see your results. That 17 mpg in mixed driving is about what I'm seeing in my '10 Tahoe, maybe closer to 18 if I'm 65% highway.

I have 2 issues with AFM operation that I think should have been addressed. First, I don't like it going into V4 mode in a cold vehicle, but it does. I would have liked to see AFM disabled until engine is up to operating temp. Second, I don't like it going into V4 mode when tow mode is engaged, or when in manual.