I had been trying to maximize time in EV mode on my commute, and had managed an average of about 46 MPG and a best of about 51 MPG using that technique. Over the past few weeks, I've been trying the high charge, ICE on mode described in this thread. (Is this the same as the ICE-High mode described in other threads?)
Most of the time, the instant MPG would max out at about 40 MPG and to push the average higher, I have been doing a mini pulse-and-glide technique. Doing this, I was able to get about the same MPGs as my prior max EV technique.
Today, I kept the ICE on instead of doing pulse and glides and was rewarded with the instant MPG climbing into the 50 MPG range, even at 65 to 70 MPH. On my evening commute, I got my new best of 53.3! I've noticed that the engine is much quieter in this mode. With my previous maximize EV technique, when the HVB is depleted and the ICE comes on, the ICE must work hard to both propel the car and to recharge the HVB. The ICE RPM range tended to fall into an area of a lot of resonance, resulting in a loud growl or mmMMMMOOOOOO-ing sound. Now, the ICE has a light load (typically just over 1 bar) and I barely hear it. Also, when I do get to a good EV section of road, the car can enter it with a full charge and go a long way.
I'm going to keep using this mode for a while to see if it gets easier to use and if I can learn the light touch needed to keep the ICE on without falling into EV mode. Minnesota's rolling hills makes it hard to keep an even throttle.