Economy is probably the last on your mind when you deiced you want a Mercedes Benz  S-Class. You probably think of the V8 model, or even one of those awesome AMG variants. But Mercedes, being a sensible car maker offers the car with a V6 as well. Now though, they’ve gone one step further and offer this big and luxurious car with a four-cylinder DIESEL engine! With average fuel consumption of 5.7 litres per 100 kilometres, the S250 CDI is “the world’s most economical luxury saloon”.

The first four-cylinder engine in the more than 60-year success story of the S-Class is also the the first car in the luxury segment to run on under 6 litres of fuel per 100 km. It also has low emissions at 149 grammes of per kilometre.

The 2.2-litre CDI engine benefits from two-stage turbocharging which makes it capable of a peak power output of 150 kW (204 hp) and maximum torque of 500 Newton metres. It accelerates the large saloon from 0 to 100 km/h in 8.2 seconds, and attains a top speed of 240 km/h.

The compact module for the two-stage turbocharger consists of a small high-pressure (HP) turbocharger and a large low-pressure (LP) turbocharger.These are connected in series, and each has a turbine and a compressor driven by this turbine. The HP turbine is located directly at the exhaust manifold and initially allows exhaust gas to flow through it; it then rotates at up to 215,000 revolutions per minute. The HP turbine housing features an integral bypass duct, which can be opened or closed by means of a charge-pressure control flap triggered by a vacuum cell. If the flap is closed, the whole exhaust stream flows through the HP turbine, so that the exhaust-gas energy is available solely for the HP turbine drive. This means that the optimum charge pressure can be built up at low engine revs.

2010 Mercedes S250 CDI BlueEFFICIENCY is priced form 71,876 Euros.