Replies

You first run on whatever electric charge is in the batteries. After that the gas engine will kick in and allow the car to be driven an additional 344 miles on a full tank (9.3 gallons) of gas.

That little gas engine runs on premium gas, due to high compression. The resulting 36 mpg is not that much to write home about, considering that a 10 year old Prius will give you 45-50 mpg on regular gas. There are also standard (non-hybrid) cars that come close to that efficiency.

The EV powertrain in a Volt is a useless, expensive gizmo that is only good for a short range. Add heater, defroster, headlights - and the battery will be flat before you leave your driveway. All the rest of the trip will be on expensive gasoline, and you will be carrying a lot of electronics around, and all these boxes will be constantly converting one kind of energy to another.

Furthermore, the gas engine in a Volt is not a backup for when the battery is discharged. It is a source of energy on its own:

Even when the gas engine is on and partially driving the wheels, it cannot operate without electricity flowing to one of the other motors.
The gas engine, under most conditions, will be used to drive the generator and produce electricity, and will not be used to drive the wheels.
There is no "direct" mechanical linkage between the Volt's gas engine and the wheels, rather there is an indirect linkage that is accomplished by meshing the power output of the engine with the power output of one of the other two electric motors.
Motor Trend's reporting that the magic cutoff speed of 70 mph is what the car uses to determine whether or not to make the engine to partially drive the wheels is incorrect. The engine is used to partially drive the wheels when the car calculates that it will be a more efficient use of the engine's power. There is no hard cutoff point.

This means that a Volt driver will hear the gas engine kicking in whenever the car decides that it makes sense. Probably that would be the case at freeway speeds.