i am fine tuning my AFR it to balance it between fuel economy and power. so far the results have been promising with 37mpg last short highway trip with NO hypermiling tactics. i'm talking just plain old cruise control set to 70mph. This included some slow downs and accelerations due to traffic:
keep in mind my car is rated 20/26 EPA. The car runs mostly 14-15 afr in cruising but sometimes lower to control temperatures and etc. here is a video of afr:
AFR and Long term Fuel Trim