Mercedes-Benz has unveiled a new concept for the evolution of the S-class luxury saloon that promises 45kpl fuel economy.

Unveiled at the Frankfurt motor show, the F125 is billed as a rolling laboratory for the sort of driveline Mercedes expects to include in future luxury cars. The hydrogen-powered research car uses an advanced fuel cell that, in theory, will provide it with higher performance than even the most powerful S-class models of today. At the same time it produces zero emissions.

The F125 also hints at styling cues for next-generation Mercedes models. The company confirmed to Autocar that elements of its exterior, including the grille and side feature lines, will be mirrored in the 2013 S-class and successor to today’s CL, the S-class coupé.

The F125 is 97mm shorter, 110mm wider and 50mm lower than today’s short-wheelbase S-class, while the wheelbase is even longer than that of today’s long-wheelbase car, due to its ultra-short overhangs.

The car has a lightweight, aluminium-intensive chassis supporting towering 23-inch wheels and weighing 135kg less than the current petrol-engine S350 CGI.

The F125 runs a state-of-the-art fuel cell system using hydrogen to create electricity, which in turn powers four electric motors providing the big saloon with the sort of pace and environmental credentials the company hopes to instil in future S-class models.

“With the F125 we want to show that large, comfortable and safe saloons with traditional Mercedes-Benz strengths have a future, partly because they’re able to operate with no emissions,” says Thomas Weber, head of research and development.

At the heart of the new system is a specially designed hydrogen tank integrated as a structural element into the floor of the F125. The electricity it creates powers brushless motors, which, installed in each corner of the car, will provide the F125 with full-time four-wheel drive.

Computer simulations suggest a 0-100kph acceleration time of 4.2sec — making it quicker than today’s range-topping twin-turbo 5.5-litre V12 S600. Mercedes puts hydrogen consumption at just 0.79kg per 100km — equivalent to 45kpl in diesel terms.