Auto News:2010 Mercedes-Benz S400

Mercedes started with the S350's 3.5-liter V-6 and added an electric motor powered by lithium ion batteries - the first in a production vehicle. The battery pack is small enough to fit in the engine compartment (the conventional battery was moved the trunk), while the 20 hp motor sits between the V-6 and the 7G-Tronic seven-speed automatic transmission. The entire package adds only 165 lbs. Engineers also squeezed more power and efficiency out of the gasoline engine by modifying the valve and camshaft timing while adding new cylinder heads and pistons. The changes net 7 hp, combining with the electric motor to make 299 hp and 284 lb-ft of torque.