AFAIK, the Chevrolet Volt (and Opel clone, etc) is the only one where the engine just charges the batteries, and the drive wheels are run by the electric motor alone.

From a technical standpoint, it's a good design for a hybrid - you can optimize each part of the system separately. But GM didn't quite get the car as a whole correct -- it has some ergonomic problems, priced higher than the value (perceived and actual) the customer got, and so on.

I actually checked before my comment. This article states that the combustion engine participates above 70 mph:

http://gm-volt.com/2010/10/11/motor-trend-explains-the-volts...

Maybe later models altered that arrangement.

^ - this. Volt fires up gas motor to optimum efficiency point to serve as a generator for the electric motor, which is the only motor connected to the drivetrain

>the electric motor… is the only motor connected to the drivetrain

This is a common misconception. The Volt will drive the wheels directly from the gasoline engine when driving at high speed (>70 mph).

http://blogs.cars.com/kickingtires/2010/10/the-great-chevy-v...

Agree, Prius and others aren't actually efficient in terms of fuel usage. And they aren't "green".

They're more efficient than the same sized non hybrid car. And define "green"

It's not about what engine size do you have, it's all about engine efficiency and how you drive. Small car can be efficient without any fancy hybrid technologies, big engine can be efficient with smart engineering.