Mercedes-Benz: Colour the Bluetec evergreen

The S350 BlueTec is one of the first passenger car turbo diesel engines to meet Euro VI emissions standards. Photo / Supplied

Such is the old-school appeal of Mercedes-Benz, it's tempting to describe the marque's flagship S-class as "evergreen".

It's not of course, and in a rarefied market segment where newest and shiniest is best, it's clear that the big Mercedes has lost much of its glamour compared with newer rivals like the Audi A8 and BMW 7-series.

In fact, the S-class, launched in 2006, is on the way out: a replacement is expected in 2013 and spy pictures are already circulating.

However, it's not time to forget about the W221 S-class just yet. Driven was invited to Australia to drive the facelifted 2011 range, spearheaded by a new BlueTec engine that's arguably the cleanest turbo diesel on the market.

The S350 BlueTec is one of the first passenger car turbo diesel engines to meet Euro VI emissions standards, which do not come into force until 2014. A substance called AdBlue is squirted into the exhaust flow to help reduce nitrogen oxides by a staggering 54 per cent over the previous car.

The S350 BlueTec has more power and torque than the car it replaces, with 190kW/620Nm, yet achieves 7.0 litres per 100km in the combined cycle - a 9 per cent improvement.

So what is AdBlue? It's the future for many diesel engines: Mercedes-Benz acknowledged the S350 could not meet Euro VI without it. Also known as AUS 32 (Aqueous Urea Solution), it's a 32.5 per cent solution of very pure urea in demineralised water. In a process called selective catalytic reduction, it's added to the exhaust flow in doses of between 3 and 5 per cent.

Such technology has been in use in the trucking industry for some time. Although there is infrastructure for AdBlue supply across Europe, potential S-class owners need not worry: the maker says that there is enough of the substance in the tank to take the car between service intervals. The AdBlue tank is where the spare wheel used to be.

Drive the S350 BlueTec and you need not worry about the extra substance and its squirting action going on underneath the car. Simply enjoy the outstanding refinement and huge wallop of torque that comes with a high-tech diesel like this. It's truly now the pick of the range - especially as there's no price premium over the S350 BlueEfficiency V6 petrol, with both at $210,000.

The petrol V6 is also a completely new engine - now with a 60-degree V instead of the previous car's 90 degree. It's a direct-injection 3.5-litre with more power and torque - 225kW/370Nm, up 12 and 6 per cent respectively - yet combined fuel consumption is down from 9.8 to 9.0 litres per 100km.

Even the V8-powered models are all about efficiency for 2011.

The S500 now has a direct-injection 4.7-litre V8 that employs two turbos to take power to 320kW (from 285kW), yet still returns 10.8 litres per 100km. As with the S350 models, the S500 features the 7G-Tronic automatic transmission.

The performance-flagship S63 AMG also boasts a twin-turbo V8 engine, this time a 5.5-litre V8 with a startling 400kW/800Nm. It has also gained stop-start technology and a staggering 27 per cent improvement in fuel economy to 10.6 litres per 100km. Not bad for a car that does 0-100km/h in 4.5 seconds - albeit with a $365,000 price tag.

The S-class: not exactly evergreen, but a whole lot more green than it used to be.