Joshua Dowling road tests and reviews the Mercedes-AMG GLS 63 4MATIC with specs, fuel consumption and verdict.

Eight cylinders, seven seats, six figures, less than five seconds to 100km/h.

And you thought landing man on the moon was an engineering marvel. How about this: a car that can seat seven occupants, tow almost 3500kg and sprint to 100km/h as quick as a Porsche?

Not all at the same time, of course. But this is still an epic breadth of ability in one package.

Put another way, imagine an Olympic sprinter with the strength to pull an aircraft. That's the best way to sum up the new Mercedes-Benz GLS 63 AMG.

It's a new, long and convoluted name that comes with a recent facelift of what we used to call the GL63 but the philosophy of the Mercedes flagship SUV hasn't changed. It's the rival to the top end Range Rovers and the new Bentley faux-wheel drive.

The acceleration is astounding.

The price of $217,900 plus on-road costs (call it $230,000 by the time it's in the traffic) may initially be enough to give you an ice-cream headache, until you realise that's less than half the price of the Bentley and about $100,000 less than top-end Range Rovers.

Not that I'm ever likely to face the dilemma but I think I just found a way to save between $100,000 and $250,000 on a car: by buying this one.

On the road

The acceleration is astounding. Responding to the right foot is a 5.5-litre V8 twin-turbo mated to all-wheel drive with seven automatic gearbox ratios.

The choice of so many gears means it can sprint from rest and then cruise barely over engine idle speed on a freeway.

Some may query why there is a 5.5-litre engine under the bonnet and a "63" badge on the tailgate. It's because the numbers on the bootlid no longer necessarily correlate to engine size.

As European regulations continue to force car makers to downsize their donks — to meet stricter emissions targets — the boffins have become better at getting more power from smaller engines.

The giant wagon feels as stable as a low-slung sports car.

It also suits the marketing departments. The theory goes something like this: "We have the same or more power than previous 6.3-litre engines so we're sticking with a 63 badge."

Fair call. In fact, this engine has greater outputs than the original SUVs that came with the "63 AMG" badge released in 2008 — we used to get excited about 375kW of power and 630Nm of torque and now we're up to 430kW/760Nm.

The other surprising aspect of the GLS 63 is how it handles corners.

Mercedes SUVs to date have not been at their best in tight bends but the new model erases previous misdemeanours.

With massive 22-inch wheels and super-sticky Pirelli P Zero tyres at each corner (nearly $1000 each to replace), the giant wagon feels as stable as a low-slung sports car.

Those who want to hear the roar of the engine will need to lower the thickened side glass, which mutes the outside world.

Only in truly tight corners does its considerable 2.5-tonne weight start to shift around. That's when you begin to appreciate the form-fitting sports seats.

Provided you're smooth with the massive amounts of power and grip at your disposal, the GLS 63 is rewarding and reassuring to drive.

Downsides? There aren't many. Those who want to hear the roar of the engine will need to lower the thickened side glass, which mutes the outside world.

At 5.1m (as long as a Holden Caprice limo) you won't be fitting into tight parking spaces.

The lack of a spare wheel of any type means you probably don't want to venture out of phone range — or tow truck range — let alone head off the beaten track. A can of goop will only save certain types of punctures; it's not much use if there is a split in the sidewall.

No doubt these will be viewed as compromises when living with one of the world's fastest seven-seat SUVs.