IN TERMS of outright sales numbers, the R-class is a mere blip on the Mercedes-Benz data sheets in Australia. But in physical size the wagon commands attention way beyond even the expectations of Mercedes-Benz Car Group managing director Horst von Sanden.

At 4922mm long for the short-wheelbase model – longer than a Ford Territory – the six-seater Benz people-mover is the answer to families looking for all-wheel drive and space without the off-road prowess of a bulky 4WD wagon.

The message seems to be working.

In its first full month on sale last month, more than 40 petrol R-classes in R350 V6 and R500 V8 guises found new homes, well beyond an initial conservative forecast 25 a month.

If this pace continues, sales will almost double the expected forecast for the first year. This has not been the case in the United States, its target market, where the R-class is suffering an identity crisis and dealers are being forced to offer incentives and been forced to lower prices.

But Mercedes-Benz has left the best for last – for now – with the arrival last week of the turbo-diesel R320 CDI, which is tipped to make up about 25 per cent of volumes.

However, Mr von Sanden said the diesel could be the volume-seller, in the same manner as the BMW X5 diesel has become the mainstay X5 model.

Offering the grunt of the V8 but fuel economy of the small V6 petrol, the R320 CDI sits in premium four-wheel drive territory with a price point of $85,900 for the short-wheelbase and $88,900 for the long-wheelbase variant.

The leviathan-like long-wheelbase version is 5157mm long, or roughly similar in size to a Holden Statesman, and all six occupants are pampered with individual seats with armrests in the second row.

Apart from its latest-generation turbo-diesel, the R-class shares its platform architecture with the new M-class and soon-to-be-released GL-class.

The twin-catalyst EuroIV-compliant V6 diesel is all-alloy with aluminium cylinder-heads, cylinder head covers, pistons, coolant pump and sump and charge pressure distributor.

Mercedes claims it is one of the most powerful six-cylinder diesels around, developing 165kW at 3800rpm and 510Nm between 1600rpm and 2800rpm.

Mated to the seven-speed 7G-Tronic automatic transmission, the R320 CDI has a combined fuel figure of 9.3L/100km. The R320 CDI will also hit 100km/h in 8.7 seconds and has a top speed of 222km/h.

The R320 CDi shares its equipment levels with the 200kW/350Nm R350 and also offers the optional $8500 touring and $8500 sports packages.

Safety is paramount and the R320 CDI list runs to dual front, front side and curtain airbags, 4-Matic all-wheel drive, Pre-Safe, active front head restraints, ABS with brake assist, ESP, traction control, front and rear foglights, parking sonar, rain-sensing windscreen wipers and a tyre-pressure warning system.

Other standard equipment includes 17-inch seven-spoke alloys, electric windows/mirrors/front seats, six-disc CD stereo, self-levelling rear suspension, a trip computer, multi-function steering wheel, outside temperature display, luggage net, height- and reach-adjustable steering wheel and direct select steering column gear selector with steering-wheel-mounted shift buttons.

And is there more to come from the R-class?

Mr von Sanden would only grin at the suggestion of the AMG-inspired R63, a 6.2-litre V8 monster developing 375kW at 6800rpm and 630Nm at 5200rpm. Stay tuned.