We like
Superlative interior quality, refinement, ride, smooth and powerful engine

Room for improvement
Fuel nozzle restrictor inhibits high-flow pump use, interior feels small, automatic gearshift awkward to use

THERE is nothing quite like sampling the best car in the world. While some may argue the relevance of a $200,000 large luxury sedan in today’s climate of uncertainty, it is clear that the Mercedes-Benz S-class carries with it immense pedigree and just a little more than its share of pioneering technology.

Most of the important pioneering technology that has been fitted to production cars has found its way to market first in a Mercedes-Benz S-class - items such as ABS brakes in the W126 in 1979, ESP in the W140 of 1995 and in the current-generation W221 Distronic Plus radar cruise control, just to name a few.

And so to the latest chapter of the S-class story - the S320 CDI. A turbo-diesel engine clattering under the bonnet of a European luxury car has been a common theme since Peugeot tucked a turbo-diesel under the bonnet of the unloved big Peugeot, the 604 in 1978, but here in Australia it is a relatively new concept.

Audi offers a 4.1-litre turbo-diesel V8 in the A8 and Q7, and BMW wants one for the 7 Series, but will wait until next year’s all-new model to release it.

Only the recent spike in fuel costs plus the news that the globe is cooking more than anybody would like has meant that owning a diesel is no longer a social taboo. No longer do you have to share the table with farmers or truckies if you own a diesel car.

The ‘new’ S-class is no longer new, having been launched internationally in 2005 and locally in 2006. The faint styling nod to the uber-sedan, the million-dollar Maybach, and a fastback coupe-style design with bold wheel-arches is perhaps an acquired taste - and certainly not as conservative a style as seen on previous S-classes.

As you step up to the S-class it looks like a big car, and at just over five metres long and just under 1.9 metres wide, it is a big car. Even if you don’t like the looks, the big Benz has plenty of presence.

Though the clipboard-carrying enthusiasts will be able to tell you bought the cheapest S-class (the S320 badge on the boot is a dead give-away) to the great unwashed this looks exactly like any other extremely expensive and intimidating German car. Which is exactly what you might want if you owned one.

Inside the big Benz the subtle hints of this being a very expensive piece of kit is everywhere. A favourite is the stitched leather dashboard - it is a sure sign that six figures were written on the cheque to buy such a car.

The aluminium and wood trimmings and cream leather everywhere, the neat hinged covered phone key pad and other well-executed touches add to the impression that this is about as high as you can go with a mainstream manufactured car.

With such an expensive car, it’s often the attention to detail that impresses just as much as the major technical advancements. The doors, for example, have heavy hydraulic struts in place of door catches.

These struts are valved in such a way that once you release pressure on the door, it will stay open in that position.

The seats are like big sumptuous armchairs and while they’re a little flat and short in the base, they are typically German in the way you can comfortably settle in for hours behind the wood veneer/leather wheel

The COMAND interface is a simple system once you have a few minutes to work it out. It has been said numerous times, but the occasional confusion that arises with BMW’s i-Drive system just doesn’t seem to occur with COMAND.

The same can’t be said for the column-mounted automatic gearshift wand, which Mercedes-Benz also uses on other models such as the ML. Despite the increase in cabin space by taking the shifter off the centre console, and despite the Mercedes ingenuity of it all, it is a pain to use. Someone should tell Mercedes wands are meant only for fairies.

Yet the S-class interior, despite the sense of occasion, doesn’t feel like a boardroom on wheels. It actually feels small, despite the tape measure telling another story completely. Perhaps it’s the swept-back coupe-style roofline, and maybe the big seats don’t help, but the headboard seems very close.

Up the other end, there isn’t as much boot space as you might expect for such a large car, although the loading lip is low and the space is neatly squared off, making it easier to pack.

All is forgiven when you start up the diesel engine, which is very quiet and takes an attuned ear to pick as a diesel.

The diesel is super-smooth too, with not a hint of vibration anywhere in the rev range that plagues other brands, even fancied German marques. Isolation, in this case, is a good quality and the S320 CDI has got it for noise and vibration suppression.

Some modern diesels have all the finesse of a highly-strung burnt-out pugilist. No finesse at all, it’s take in a big breath of lag followed by a sucker punch of mid-range torque and an out-of-breath top-end.

It’s all over in seconds, and such vehicles - there’s more than one - are often hard to drive smoothly with that erratic torque delivery.

The S320 CDI is nothing like that - it delivers its performance in a relatively measured, linear way for a turbo-diesel, with the turbo-lag a reasonably muted segue into the mid-range and the tacho flicking to the top-end for a neat finish before the creamy-smooth seven-speed automatic slides into the next ratio.

It’s no free-revving big petrol V8 engine, but in the first two-thirds of the rev range its makes a passable impression of such an engine.

The seven-speed auto has a very short first gear, which together with the variable-geometry turbo may explain the small amount of turbo lag.

Fuel consumption reached 12.0L/100km on the launch drive, although one of my collegues said his trip computer was showing 10.0L/100km at the end of the drive. Not bad for primarily urban running.

Not so good is the restrictor in the fuel filler neck. Intended originally - in Australia at least - to stop people putting leaded fuel in unleaded cars when ULP was introduced (leaded nozzles would not fit due to the fuel neck restrictor), the use of this in a diesel car does not make sense.

This is especially since the small nozzle diesel pumps are not found at all service stations - instead the large nozzle high-flow bowsers that trucks use is sometimes all you can find. It means a long, messy, slow refuelling process if you must use a high-flow bowser.

The big Mercedes is a heavy car (though at just under two tonnes is relatively light for a large prestige car), yet feels adroit on the road, with its combination of assertive acceleration, strong brakes and stable dynamics.

Steering precision is spot-on, even though feel through the leather and wood wheel could be better, especially on-centre.

Height-adjustable air suspension can be difficult to engineer properly for a smooth ride, yet on the S-Class it has succeeded - no doubt helped by the standard 17-inch wheels on relatively tall 235/55-section rubber.