I got the edge CTS and that helped my MPG a bit as well. When I am running the premium tune I went from 13.5MPG in town to 16.5. This is no joke. Also from 14.5 Highway to 18-20 depending on wind, i live in KS, and how fast I drive. Yes you get much better MPG at 65 then 80
I lowered my torque converter lockup in 4th down so I get it locked up at 40-41MPH. Most of my driving is 45 MPH. Before it would lock and unlock quite often. Also I have it holding in 2nd and 3rd gear longer. It is now where it should be in my opinion. As before it felt like it was lugging along, then to finally get it to get up and go it would be about 3/4 throttle. Now its responsive and quick and much more drivable.
Honestly I wasn't expecting any increase in MPG. The power increase is just fantastic and the overall drive-ability is beyond improved. I got mine used on ebay for a great price.