Just as a reference for what decent weather can do for you, I live in Southern
Florida where the temps have been in the 70's without reformulated fuel.
I picked up my 2006 HCH on Tuesday and have avg. 52 mpg for 200 miles (40 mile trips).
The mpg reading is per the digital indicator haven't completed a tank for manual comparison yet.

Mostly highway driving (heavy traffic in evening commute), and some city.
Some small hills on the highway but for the most part flat.