GM takes two-way road on hybrids

The performance challenge with this sort of system is that the electric motor/generator is attached directly to the gasoline engine. The two are locked together, and one can't move without the other.

In the first-generation version of GM's light hybrid system, that meant the car would abruptly slow as soon as you lifted your foot off the gas. Brake performance was wobbly and uneven as automatic downshifting was used to push the motor/generator (to generate electricity) and the 4-cylinder engine with it.

In the newer version - now available in both the Malibu and Aura - the hybrid performs like a regular car, except that the engine shuts down altogether whenever it stops. Deceleration and braking are smooth, with only occasional unevenness during slow stops.