Frankly, GM's experiment in mild hybrid sedans didn't go so well. The automaker had produced a mild hybrid version of the popular Chevrolet Malibu, but sales volumes were low and the program has been discontinued.

Chevrolet manger Ed Peper admits GM learned its lesson.

"One of the issues with the Malibu hybrid has been that the four cylinder 6 speed transmission Malibu gets 33 MPG on the highway," he said. " It has the best fuel economy of any mid-size car out there for a normal gas engine, so it makes it that much tougher to make a hybrid that gets significant better gas mileage than that."

The 2009 4-cylinder Malibu has an EPA rating of 22 MPG city | 33 MPG hwy. The 2009 Malibu hybrid gets 26 MPG city | 34 MPG highway. It uses GM's first generation mild belt-alternator-started hybrid system.

"Consumers are not going to pay for it unless they can get significant better fuel economy," he said.

Peper disclosed to that GM is now working to develop an extremely fuel efficient dedicated hybrid besides the Volt.

"What we are trying to work towards is 'Yes,' we will have other hybrid vehicles (besides the Volt) but we are trying to work towards a dedicated hybrid," he said. "We think that’s probably a better way for us to go longer term."

"I think when we bring out a hybrid, and I think its very important, we've got to make sure it has significantly better fuel economy than a non-hybrid," said Peper.