Autocar understands the final CO2 figure of the S500 Plug-in Hybrid, as the model will be known, will be just 70g/km in order to trump the 71g/km figure of current lowest CO2 emitter in the luxury saloon segment, the Porsche Panamera S E-Hybrid. Economy is expected to be above 90mpg on the combined cycle.
The model, previewed at the media launch of the new S-class in Toronto — ahead of its full reveal at Frankfurt — will mix a V6 petrol engine with an electric motor and a battery pack mounted in the boot. Some boot capacity will be lost to the batteries.
The S500 Plug-in Hybrid will be the third and most efficient hybrid in the new S-class line-up. Others offered include the not-for-UK petrol-electric S400 Hybrid and the S300 BlueTec diesel-electric hybrid.
Mercedes sold more hybrids than all of its luxury German rivals put together last year. It sold 20,000 hybrid versions of the previous-gen S-class, 60 per cent of which were in China.