[MetroMPG]

My understanding is that even the Volt will use a defined lower SOC threshold on its battery, permitting discharge only to a certain level (albeit likely a deeper one than the Prius) before the generator starts.

So the Volt engineers/drivers could theoretically face a similar situation: if the ICE runs out of fuel when in charge-sustaining mode, the batteries will still have energy in them. How much will the driver be permitted to use once the gas is completely gone?