Interesting numbers! I left on 2 May going from Columbia, SC to near Madison, IN, and for a round trip total of 1071 miles (returned yesterday), I averaged 58.6 mpg for the trip. I set the cruise at 60 mph and did let the auto climate run the whole trip. All except for perhaps 108 miles is interstate. I did not re-fuel at the same pump locally upon my return, and am personally a little cynical of 58.6, but am comfortable that I did get in excess of 57 mpg. A few more trips will give a better feel...
BTW, it added about 1.5 hours each way on my drive with my speed reduced to 60 mph. Well worth it to me!

 

When we drive from Charlotte, NC to Cherry Hill, NJ, I insist we drive no faster than 65. I'll speed up to 65 and try to maintain roughly 75 mpg on the IFCD until I hit 60 mph and then speed back up again. It's about a 535 mile trip and the best we would get is 56 mpg. That's with a fully loaded trunk, my wife and the 2 small kids.