So being stuck in the low to mid since I got my car about 3 weeks ago I think I finally got it. Today I drove 27 miles and got 63.4 mpg.
Keep in mind, you might get high mileage on a trip due to winds and elevation change. If that 27 miles was one way, it'd be interesting to know the mileage in the other direction. Google Earth can give you an elevation profile of a route between 2 points! | PriusChat can help w/the determining/plotting elevation change.
I actually doing a lot better regarding mpg did a46 mile trip on freeway and got 52.8 with ac and driving semi fast.