I can't say I'm surprised by this but it turns out GM have been lying to everyone about the Chevy Volt. Turns out that the petrol engine actually can (and does) drive the wheels. In other words, it's nothing more special than a hybrid vehicle. This is exactly the opposite to what GM have been telling the world right up to this morning. The most recent re-iteration of this point came in June, when GM spokesman Rob Peterson told AutoblogGreen that there was "no mechanism in the Volt to drive the wheels even if the engineers wanted to". (source).
Motor Trend got to test drive a Volt for the first time and observed that the petrol engine did indeed drive the wheels. Mechanically, it's not separated from the driveline as GM had indicated. Quite the opposite; it's connected to one of the motor-generators which is in-line with the drivetrain.
What about that amazing 230mpg claim then? Well obviously that also turned out to be a lie. Real-world figures for the Volt are coming in around 25-30mpg city and a max of 37.5 highway (Popular Mechanics). 37.5 is not 230. It is however worse than a Prius, and worse than a non-hybrid Ford Focus.
This is potentially suicidal for GM. They lied about the Volt's motive power source (which presumably means they also lied about the "common" platform it's built on where everything is hidden in the floorpan). They lied about the gas-mileage, and the final vehicle is nothing more than a hybrid - one that is already outclassed by dozens of other non-hybrid vehicles. Why would anyone buy a Volt now?