The conclusion that running in pure EV mode wastes energy is wrong. It all depends on particular situation. Just to give very simple example, last mile of your trip should be driven in pure EV mode if possible, leaving battery in low state of charge, the next time you start the car, the cold engine will run constantly until fully warm regardless of the state of battery charge, if the battery is fully charged, then all the energy goes to waste , if the battery is low, then engine will charge the battery almost for free so to speak. Also you never took into account the fact that gasoline engine is much more efficient under heavier load, so you may loose efficiency due to multiple energy conversions, but gain efficiency by loading the engine more, especially during lighter power demand and recharging the battery at the same time. There is something called pulse and glide, used by hypermilers to increase FE, driving partially under EV mode and partially under ICE power would be a sort of milder version of that technique. It's all academic anyway because above 42 miles per hour, the ICE will never shutdown anyway and under 42 MPH in normal driving conditions, at least where I live, you pretty much depend on the traffic conditions and drive as other people let you, not the way you want. I write this just after driving 30 miles, actually sitting in traffic for 2 hours in rain, so I hope you know where I'm comming from. BTW I can't find it at the moment but I believe I read somewhere the Synergy drive has efficiency higher than 90%, therefore in a lot of stop and go traffic, using EV mode I believe you'll cover conversion loss of efficiency with higher energy absorbtion during breaking, empty battery will take in more energy than fully charged one.