Oddly for a hybrid, my vehicle performs better on the highway than in the city. Even without the Oh So Special Traffic Conditions that permitted regular 30MPG tank averages.
This is from Massachusetts to New Jersey. Premium fuel was used as an experiment. No modifications have been made to the vehicle. The only difference from "normal" drivers was letting my foot manage the throttle instead of the cruise control.
Speed was 55-65, venturing above 65 only on large downhills (before I hit the brakes to capture some of that "free" energy). If climbing a hill, I held 50MPH. Considering I basically committed every hypermiling sin imaginable (holding on hills, A/C on, not-going-under-55, no blockers) I think I did pretty well.
Given my car's computer's typical inaccuracies, I'd say the "pump" MPG will be within the range of 31-35.