Mercedes may be working on a new Mercedes-Benz SLK Gullwing hybrid, going 0-60mph in under five seconds, while getting good gas mileage.

Mercedes is currently working on a new sportscar to be slotted under the SLC supercar. The new Mercedes-Benz SLK Gullwing would be a hybrid, with an all-electric range of 120 miles, according to Auto Express.

The decision to make the top-of-the-line SLK with doors hinged in the roof had to do with battery placement. Mercedes is believed to want to put lithium-ion battery packs in the side sills, which would need to be raised higher to accomodate. This could be the same li-ion system seen in the Blue Zero E-Cell concept at this year's Detroit Auto Show. Regenerative brakes and a stop-start engine advance the hybrid system one step further.

Not many cars could get 40 mpg, and generate a relatively clean 150g of CO2 per kilometer, while maintaining a 0-60mph time of five seconds. That power comes thanks to an advancement on the current 3.5 liter V6 petrol engine. The current version produces 300 hp and up to 266 ft-lb of torque. Top speed of the new rear-wheel-drive would be around 155 mph.

With the new SLK lineup planned for a 2011 release, it is likely the Gullwing would come out later. If it gets the go-ahead, the new 2012 Mercedes-Benz SLK Gullwing would be a competitor to the Porsche Cayman S and the Audi TT RS.

Gallery: Mercedes SLK Gullwing in the works?