The way I got 15 more mpg was to save ev use for maintaining and coasting. I also rode the brakes to a stop hard enough to fully lite up the brake part of the indicator. I also fully inflated the tires to sidewall psi.
Ive gotten a lot of nasty emails about my rip of the useless ev switch too on a youtube video I made of my test drive. Infact during the test drive Ive pressed the button several times and got one message after another as to why it couldnt go into it. Then, looking at the screen, half the time it appears the ICE was off and it was on battery and that was even at highway speeds.
I never let the idling bother me at low speeds. It was explained to me the drivetrain is geared too high for the ICE to drive the car below 10 mph and it was better for it to spin using mg1 to top off the pack and mg2 to move the vehicle and the coolant heating up, blah, blah, blah.