Mercedes-Benz is reported to be developing a new version of its S-class limo equipped with an ultra-efficient Bluetec diesel engine. With a motor displacing just 2.2L, the new diesel driven S-class should return a fuel economy rating of just 6.6L per 100km, or roughly 35mpg.

We should get our first glimpse of the new car at September’s Frankfurt Auto Show, with production scheduled to start towards the end of next year. Germany’s Auto Motor und Sport reports that Mercedes will be combining the four-cylinder oil-burner with its new mild-hybrid system to achieve the amazingly low consumption figures.

Mercedes previously showcased a Bluetec hybrid S-Class concept at the 2005 Frankfurt Auto Show, but unlike the concept car which featured a V6 powerplant, the production version will run a twin-turbo four-cylinder motor that produces 204hp.

The vehicle will be in full compliance with future Euro 6 emissions standards, which are expected to roll in by 2014, and we should see its efficient powertrain eventually offered in the E and C-class range.