MERCEDES-BENZ has been just a little surprised by the number of folk that have lined up to drive away in its new R-class.

Sales are well above initial expectations and none of the doubts that have dampened United States sales are being experienced here.

It seems many Australians love the idea of an all-wheel drive wagon that seats six people in superb comfort yet offers all-wheel drive and a commodious cabin.

Those looking at the badge and seeking a conventional wagon can also still get into an E-class wagon but the R-class has size on its side.

Of the three models – R350 V6, R320 CDI V6 and R500 V8 – the turbo-diesel is the pick of the bunch.

With around 2.2 tonnes to haul, the turbo-diesel - mated to the silky seven-speed auto - is just the engine to give the R-class some athletic acceleration but does not ignore economy in a day, and age, when the price of fuel is becoming an increasing talking point.

The all-alloy 24-valve R320 CDI engine boasts the very latest in turbo-diesel technology.

The 3.0-litre V6 pumps out 165kW at 3800rpm and 510Nm from 1600rpm, representing something of a performance powerhouse in both everyday and highway driving.

Importantly too, the R-class’s hefty weight is never an impediment to the performance of the turbo-diesel, making the diesel the preferred choice in this car.

The V6 is equipped with the latest-generation common-rail direct fuel-injection technology, meaning the injectors, high-pressure pump and electronic engine management systems work more efficiently. This helps reduce fuel consumption, emissions and noise.

The lack of noise is an interesting aural revelation.

At idle the diesel sounds like a slightly more muscular petrol V6. There’s never any indication that the package is diesel.

Once under way, the R320 CDI impresses with its low-down power and torque and strong highway overtaking response. Quietness is a byword too.

In the cabin, the occupants are blissfully unaware of what’s powering the wagon as it slices through the air.

There’s little wind, road or suspension noise. In typical Mercedes fashion, the cabin is cocooning and all but the most aurally sensitive person would not recognise that the engine is a diesel.

We’d perhaps prefer some more feel in the steering as the R-class exhibits that typical Mercedes numbness through the steering wheel, particularly on the straight-ahead.

But the brakes, ride and handling are all as one would expect from the big German car-maker and the rear parking sensors are a welcome standard inclusion.

Our R320 CDI was equipped with the optional ($3450) Airmatic active damping system, which combines with the semi-active air suspension to add just a little more controllability to the car when push.

With the system the R-class can be hustled through corners in a similar fashion to a much smaller sedan. It provides a degree of responsiveness and precision that is greatly appreciated and belies the car’s overall on-road mass.

As it is, based on the M-class and GL-class SUV platform architecture, the cabin and interior borrow much from this four-wheel drive.

The driving position, commanding view and ergonomics are first-rate, making the R feel much like just a large wagon.

Rear passengers are spoilt for space and comfort, courtesy of the individual seats and all the rear seats fold out of the way if you need extra load space.

The centre console between the second row of seats is a nice touch, but at $1250 seem an expensive option for what amounts to a couple of cupholders and some storage space.

The car boasts a striking, overly large grille with long, horizontal louvres and a steeply sloping bonnet that dominates the front.

In profile the R-class has a very tall roofline that arches from the mudguards right through to the rear. The overall look is pleasing and stylish and the car is reasonably authentic to the original Vision GST concept car upon which it is based, except for the "suicide" rear doors on the concept car.

Mercedes quotes an overall fuel figure of 9.3L/100km for the CDI, which given its size and weight, is impressive. We managed around 9.0L/100km on a mix of city and highway driving and it is clear that once the diesel V6 gets a few more kilometres under its belt economy will be a strong point.

The 80-litre fuel tank will ensure long distances between refills.

For the performance-minded, the R320CDi is no slug. It will also hit 100km/h in 8.7 seconds and sail on to a top speed, where permitted, of 222km/h.

A wolf in sheep’s clothing it may not be, but the R320 CDI certainly is a surprising package.