We like
Interior space, full-size third-row seating, luxury appointments, safety features, breadth of on/off-road ability, value compared to M-class

Room for improvement
No full-size spare wheel, road-side third-row access, no separate-opening rear glass, noisy air suspension off-road, dull steering, intimidating size and weight

NO LONGER must Mercedes-Benz buyers look to other brands to sate their appetite for a full-size seven-seat SUV.

That’s right, just when it appeared Benz had missed the seven-seat SUV boat by offering seating for just five with its second-generation M-class, which has been on sale here for more than a year and was recently joined by Audi’s seven-seat Q7 (BMW will also join the seven-seat SUV craze with its MkII X5 next April), along comes the M-class derived GL-class.

Bigger in all key dimensions than the M-class upon which it’s based, bigger in all areas (except width) than its key rivals in Q7 and the next X5, and offering more interior stretching space than the short-wheelbase R-class people-mover it’s built alongside in the US, the all-new GL-class can seat up to seven full-size adults in luxurious comfort – and go almost anywhere a Range Rover can.

Available in Australia as standard with the same Off-Road Pro pack that costs about $10,000 extra for M-class buyers, the entry-level GL320 CDI turbo-diesel commands a $13,000-higher sticker price than the equivalent ML320 CDI. But a third row of seats still adds at least $3400 (including mandatory 19-inch wheels and power operation) to the GL’s price, which equates to a reasonably modest $6250 price premium over the M-class at base level.

For the $104,000, the GL320 CDI offers a lot of metal. Featuring two prominent "power domes" in its bonnet and unique sheetmetal, there’s no escaping the sheer size and road presence of the new GL - even when it’s not jacked up to its full 307mm of ground clearance (14mm higher than the Off-Road Pro-equipped M-class). When it is, it’s a L-O-N-G step down to the ground.

Inside, a longer wheelbase than a Statesman affords excellent stretching room for all occupants - including third-row passengers, who benefit from two (optional) full-size seats that provide class-leading head, shoulder, hip and leg room.

The rearmost seats fold open and closed individually at the push of a button to allow access from the rear, and even with them up there’s still enough space in the cargo area to store a couple of soft bags. With them folded flat there’s an enormous amount of luggage space available, and with all but the front seats folded the GL will carry more than a Commodore or Falcon wagon.

The GL also offers five litres of extra fuel capacity over the M-class (100 litres verses 95), and gains extensive woodgrain trim highlights.

Out back, there are two well positioned scuff plates on the low, flush loading lip and the large but reasonably lightweight flip-up tailgate features a handy self-opening/closing function on the V8-engined GL500 (it’s optional on the diesel).

Of course, all seats offer the safety of a three-point seatbelt and adjustable head restraints.

Interior downsides? There’s no separate-opening rear window, the 60/40-split second-row seat doesn’t slide and the centre row’s single folding seat to allow third-row access is not positioned on the kerb side.

Surprisingly, as with M-class, there’s no full-size spare wheel either, but Benz says it’s still working on an external spare carrier for both the M and GL.

On the road, there’s no hiding the GL’s 2450kg kerb weight. The GL320 CDI is not as spirited as the 250kg-lighter ML320 CDI, which requires less anticipation for ambitious overtaking manoeuvres.

As such, the high-tech 3.0-litre turbo-diesel V6 must work about 1000rpm harder to achieve similar results, but the superb seven-speed auto still extracts enough from it to make the GL320 an effortless open-road tourer.

As expected, despite the fact it offers just 20Nm more peak torque, the GL500’s new 5.5-litre V8 sounds and goes better, and makes the M500’s three-valve 5.0-litre engine (which should be replaced by the GL’s new V8 around September next year) feel lacklustre in comparison.

Driven sensibly, the turbo-diesel GL-class should have range of more than 1000km. Combined with the highway commute from Brisbane, Fraser’s hard, sandy going saw our GL320 CDI average a respectable fuel consumption figure of 13.9L/100km, while most GL500s finished at around 18L/100km after spending much of the time in 20s.

For the extra $43,000, the GL500 offers more than just extra urge by featuring useful standard features like 19-inch alloys, Nappa (not faux) leather, Comand with sat-nav, three-zone climate-control, a self-closing tailgate, active bi-Xenon headlights, a sunroof, heated/memory seats and auto-dimming mirrors.

Options like Distronic radar-cruise, a TV tuner, a rear-seat entertainment system and keyless starting potentially make the GL-class one of the finest family vehicles around. But, while a full compliment of safety equipment (including twin front, front side and full-length side curtain airbags) is a given, the optional reversing camera should be standard in an SUV this big.

Like most Mercedes models, both X164-codenamed GLs offer steering that’s so well isolated from road shocks that it lacks feel, especially at low speed, and there is some initial bodyroll when pitched into corners. The big GL never keels right over in corners though, no matter how hard it’s pushed, but can feel unwieldy if throttle and steering inputs are less than fluid.

Wind noise and ride comfort is exemplary, but in sport mode the variable suspension damping can be somewhat jiggly on coarse road surfaces.

Fitted as standard with Benz’s off-road package, both variants offer four positions of air suspension ride height (including an automatic mode, which selects the lowest possible setting at highway speeds), plus front and rear underbody protection, centre and rear differential locks, and a push-button low-range transmission ratio.

Positioned on the right-hand steering column stalk, the P-R-N-D gearshifter is supplemented by "Direct Shift" buttons on the steering wheel, which provide convenient one-touch manual override.

With more ground clearance than just about anything, the GL was the perfect device for traversing Fraser Island’s deep sand tracks on the launch. Reasonably short overhangs and an impressive ramp-over angle prevented it scraping its bodywork or underbelly anywhere, which is something few seven-seat SUVs can claim, and its electronically controlled permanent all-wheel drive system maintained traction and momentum on even the softest of inclines.

But all the electronic gadgetry in the world is pointless unless the wheels have traction, and although the GL was never caught short on Fraser Island, we suspect the superior suspension travel offered by the likes of Range Rover and the similarly sized Discovery would see them leave the GL in their wake when the going gets really serious.

As with the M-class, the GL’s only shortfall off-road is the disconcerting noise the suspension makes when its wheels "top-out" fully under rebound. A constant annoyance on Fraser, where it took the shine off an otherwise faultless performance, it’s a distraction that’s not evident on other air-suspended SUVs.

Of the 400 GL-class vehicles it plans to sell in 2007 (a fraction of the 2500 M-class sales expected next year), about 100 are expected to be five-seat versions. That’s surprising, given the equivalent Off-Road Pro-equipped M-class is cheaper, just as accommodating and just as capable both on and off-road.

Some of those buyers will use the extra cargo space the GL offers over the ML, but we suspect most simply want the biggest, most expensive Mercedes SUV available.

For them, the GL-class is in a class of its own.