Mercedes S350 CDI BlueEfficiency LWB (2010)

What puts the BlueEfficiency into the Merc S350 CDI?

A suite of small changes are designed to make the S-class more efficient. The automatic transmission disengages at a standstill, for instance, reducing the load on the engine and quietening things down; it re-engages the second you take your foot off the brake. Lower rolling resistance tyres are pumped up to 2.6 bar, while smoother door mirrors, headlamp seals and an undertray drag the aero figure down to 0.27. It’s a slippery customer, the new S-class.

The result? The S350 CDI averages 37.2mpg and pumps out from 199g/km of CO2. Our particular BlueEfficiency model was the lounge-worthy LWB model with a rather confusing Eco-Power Engine Kit (a £1584 performance upgrade pack – on a green eco special!) that nudged consumption and emissions up to a still impressive 36.7mpg and 204g/km.

So is the S-class still a smoothie to drive?

You bet. It’s easy to see why the S has become the default choice for limo buyers in this market. It’s a brilliantly comfortable place to sit, with excellent seats that adjust every which way, intuitive infotainment systems and a hushed whisper that makes it hard to believe you’re powered by diesel. It’s massive in the back, and the quality of leather, wood and fittings is outstanding.

The S350 CDI is so relaxed and pampers away the worst road scars, isolating occupants in a hermetically sealed leather lounge. Although I’ve yet to drive the new A8, in my mind the S-class must be the most refined of the class. The 7-series may be more dynamic and the XJ set the dynamic benchmark for enthusiastic drivers, but there’s something uniquely pampering about the big Merc limo.

In fact, I’d question the need to buy any other S-class. This base model has ample performance (7.8sec 0-62mph, but it feels faster in the mid range) and you’d need to be in a huge hurry, or have more money than sense, to choose one of the larger petrol or AMG models.

What about all these new gadgets?

It’s the usual Merc fayre: gizmos that we’ve seen elsewhere have finally been added to the S-class, such as adaptive high beam, a system to check for driver drowsiness, night vision that picks out pedestrians and a Splitview monitor so driver and passenger can watch different screens on the multimedia device.

We might worry about the longevity of these systems in future (would you buy a loaded 2010 S-class in a decade or two’s time?) but there’s plenty of fun to be had tailoring your exact spec of car to meet your needs.