I have a steep downhill for several miles., normally I can pick up 4 -5 miles of range. Yesterday I had zero electric miles and gained zero miles. I was afraid to put it in electric mode at the top in heavy traffic, what would have happened?
Note that if your estimated ev range increases 4-5 miles by the time you reach the bottom of a hill, it means your downhill mileage is better than your level terrain mileage, and as long as you keep driving downhill, that improved mileage would allow you to drive further than if you return to driving on level terrain. Since you had no ev range to modify, did you note any change to your gas range estimate?
If you drive far enough to fully deplete your battery, you can’t switch back to Electric Mode because all the useable grid electricity stored in the battery has been used. "Electric Miles" are miles driven using the grid electricity stored in the battery, and any regen obtained while driving in Electric Mode. Once it’s depleted, it’s gone, and you’re in Extended Range Mode until you recharge from the grid.
Regen is potentially possible whenever you are not using the accelerator pedal to maintain or increase speed. Driving Mode doesn’t change the Volt’s ability to create regen. You can drive as far on 1 kWh of regen battery power as you can on 1 kWh of grid battery power.
If you drive in Normal in Electric Mode to the top of a mountain, and fully deplete your battery before you reach the summit, the ICE starts, you’re still in Normal and now you’re in Extended Range Mode. There is no way to switch back to Electric Mode because that requires having useable grid power in the battery, and you now have none.
You then start down the hill... when you reach level terrain again, the battery SOC is now well above the "fully depleted" level because of regen. The ICE is no longer running, not because you switched the driving mode, but because the battery SOC is above the minimum level. You then drive on battery power until the battery SOC drops again to the "fully depleted" level.
This downhill regen may provide you with several miles of battery-powered driving. The ICE is not running, you’re not burning any gas now.
So, are you at this moment driving on "electric power" or not?
Or - because the Gas Icon is still active on the display and Gas Miles keep increasing - do you think your ICE is still running?