I just got back from a trip from Oakland to LA and I was averaging 22+MPG going 75mph. (the fuel economy bar was all the way to the right) I was stoked to have made it on one tank.... I noticed that the key was to keep the adaptive cruse control on. It seemed to be in eco mode all the time while in cruise control. Over the grapevine, it was down to 13MPG and in the city I am getting about 15MPG. I am at 2750 miles now.
2011 Black Jeep Grand Cherokee Overland Summit Edition- 4x4 5.7L
2006 Red Jeep Wrangler Rubicon - 4x4 4.0L