The 06 HCH is advertised as being able to run in electric-only mode 'under certain circumstances during low-speed cruising', but I've never seen anything that defines what those circumstances are.

Since there is no 'EV' indicator on the dash and there is no perceptible sound or vibration difference when running in electric only mode, I'm defining 'EV mode' as the state where the instant MPG gauge is pegged out at 100mpg and one or more bars of assist are showing. Based on my observations of the instant MPG gauge alone (is there a standard GreenHybrid acronym for that?), the ECU seals the valves and cuts off fuel to the ICE whenever I take my foot off the gas, but only if there are assist bars showing (and the car's speed is maintained) is the electric motor actually propelling the car forward.

Anyway, I tried several times last night in my neighborhood to enter the magic 'EV mode', but to no avail. Maybe it's because the car is brand new, or maybe it was because of the lower temps last night (low 50's). Today I had much better success (70's). It always happened in the 25-30 miles per hour range and I had to hold the accelerator very steady. The slightest extra pressure or moderate incline would make it start sucking gas again (instant MPG no longer pegged at 100). But, as easy as it was to go out of EV mode, it was also easy to get back in. I was able to sustain it for up to 30 seconds at a time, but I usually lost it because of environmental factors (incline, traffic, etc.). Once I was even able to sustain it up a small incline (3 assist bars)!

The ECU seems to be very efficient at only flowing the gasoline when it absolutely has to. And, since the ICE remains spinning, there's no overhead associated with spooling it back up. I would guess that on a closed, flat course an experienced hypermiler might be able to sustain it for long periods (perhaps limited only by the current battery change) and get a LOT of miles out of a tank.

Did I mention that this car is loads of fun?