According to Car and Driver, these are the engine choices:
Internally referred to as W222—long-wheelbase versions carry a code of V222—the 2014 S-class will be launched this fall with a twin-turbo 4.7-liter V-8 that produces 455 horsepower and 516 lb-ft of torque. An all-wheel-drive version will follow a few months later, as will the ?ber-high-performance S63 AMG. Next year, two V-12–powered models will be added to the lineup: the S600 and the stupid-powerful S65 AMG. Other markets receive a V-6 hybrid, a V-6 turbo-diesel, and a four-cylinder diesel-hybrid that consumes fuel at a level similar to that of a Toyota Prius. Some of these models could be offered stateside some time down the road, but for now, the focus is on the higher-performance models. The only available transmission is Benz's smooth-shifting seven-speed torque-converter automatic.
For both rear- and all-wheel-drive V-8–powered S550s, Mercedes claims the 0-to-60 sprint will take 4.8 seconds. Top speed is governed at 130 mph, which is 25 mph down on the governor set for European models. No U.S.-market fuel-economy figures are available yet; in Europe, the S550 is rated at an excellent, albeit inflated, 27.4 mpg.
Edit: The V-6 Hybrid is called the S500.