The latest and greenest version of Mercedes' flagship sedan makes its first public appearance in Frankfurt and promises to deliver stunning fuel economy coupled with unprecedented CO2 emissions marks for a vehicle of its size. Based on design elements first found in the Vision S 500 Concept that Mercedes presented in 2009, this third and most sophisticated S-Class hybrid variant goes on sale next year. It will arrive in the U.S. as a 2015 model and effectively replace the current S 400 Hybrid.

Based on the all-new version of M-B's luxury 4-door, the S 500 Plug-in Hybrid features the latest iteration of the automaker's hybrid drive system. For this application, it teams a 3.0-liter turbocharged gasoline engine that makes 329 horsepower and 354 lb-ft of torque with an electric motor that develops 107 horses and 251 lb-ft of peak twist. When both power sources are operating together, the S 500 Hybrid can sprint from 0-62 mph in just 5.5 seconds and reach a top speed of 155 mph. If it's running in pure EV mode, the trunk-mounted lithium-ion battery pack holds sufficient juice to let the S 500 Hybrid travel nearly 19 miles in on a single charge.

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In addition to those two options, S 500 Hybrid drivers can select an E-Save mode that reserves the fully charged battery for use at a later time or a supplemental Charge mode that allows the pack to be replenished while the car is being driven. One key to the overall efficiency of the new S 500 Hybrid - it returns an amazing 78.4 mpg overall on the less stringent NEDC test cycle as well as an unprecedented 111g of CO2 per mile - is the car's new Gen II recuperative braking system (RBS).

With RBS, any time the brake pedal is depressed, initial deceleration is done by the electric motor which immediately swings into alternator mode to provide simultaneous braking and charging functions. Depending on driving conditions, RBS decides the best balance between slowing via the alternator effect and using the car's conventional stoppers which are then seamlessly interfaced to ensure minimum braking distances. The gas engine shuts down completely whenever the vehicle is coasting and its drag torque gets converted into recuperation torque that allows the S 500 Hybrid to effectively "sail." The RBS also is programmed to use the combustion engine as an active charging element as little as possible, and then only when it can be done in an efficient manner.

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The new S 500 Hybrid further maximizes its total efficiency through the use of an intelligent anticipatory energy management system. Capable of looking ahead by roughly five miles to assess upcoming traffic and topographic conditions which are culled from the car's navigation and COMAND telematics systems, it then optimizes the battery charge-management based on the projected driving route. Beyond offering remote smartphone control of various system functions and fast external charging capability, the 2015 Mercedes-Benz S 500 Plug-in Hybrid also boasts a haptic accelerator pedal that provides tactile feedback whenever the gas engine is activated to help the driver manage its use more efficiently.

More Hybrid Cars...

The 2014 Honda Accord Hybrid goes on sale here this fall

The 2014 Porsche Panamera offers a plug-in hybrid option

Toyota and Lexus hybrid sales have topped over 5 million worldwide



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