186.8 miles for a full charge and a challenge for you my fellow Volt owners, only if you have time to spare. Most of us are assuming that if you have an all downhill road, the Volt's range can be infinite. But we all know that there's no such thing as an all downhill road. So from our area here in Northern California, I took up the challenge to see how far I can glide downhill on a single full charge of battery. It is one thing to speculate how far, and still another thing to do it in real life.
And starting from the charging station, I was able to achieve 186.8 EV miles on my 2017 Siren Red Volt on a full charge before the gasoline engine switched over. This is an astonishing 13.25 miles per kWh using only 75.5 Watt-Hour per mile for the entire battery pack on mostly downhill run.
I challenge you to find your own hill and beat my score and post it here, to try to push the limits. You may find that your speculation of downhill having infinite miles really don't hold water or electrons for that matter.
To help you in this challenge know that the Volt is about 3519 lbs and assuming the person driving it is 175 lbs, for each 1,000 ft of elevation change, there is a potential energy difference of 1.392 kWh. A full battery pack of the Volt has 14.1 kWh usable state of charge. A difference of 10,135 ft equates to 14.1 kWh. Now you'll have to add more height to account for losses in rolling resistance (depending on tires and road condition), internal resistance, air resistance losses (depending on speed and prevailing wind), and just assume air temperature remained optimal at 85 deg F for the battery.
If you're in California, here's a listing of all mountain pass roads that you can drive your Volt to and to use to glide to beat my score. But you would need a charging station near to your chosen hill.