There is also an issue of steady-state driving vs. real life. Its rare that you drive under the same conditions for long periods of time, except for long highway trips. Thus, it is relevant to consider what your driving conditions will be like 15 minutes from now when considering how much to favor the ICE vs. electric motor. For example, on my 70 min commute, I'm often stuck in sluggish (20-30 mph) traffic on the DC beltway, but I know that in 5 or 10 minutes I'll be cruising at 70+ mph and the ICE will be able to efficiently recharge the battery. Under that scenario, I think its favorable to go full-electric in the slow traffic. Not to mention safer, too. Longer traffic jams ultimately take their toll because you have to recharge the battery under low-load conditions.

Maybe pulse & glide at all times would be more efficient, but its not always practical. I do know that I get better mileage on the days I'm stuck in traffic and favoring stealth mode.

-Terence