I had one of the early plug-in Priuses. Bought it with 150K miles on it. Battery had degraded so I only got 12-18 miles on battery, but I was getting 65+MPG around town, less at highway speeds. I didn't consider 65+ to be particularly inefficient. That car got totalled and I'm back to a standard Prius v (the wagon). I get around 50MPG, which I'm not super happy about. I *suspect* the better mileage of the plug-in is from the larger battery pack, so more energy stored from regenerative braking.