Now, half way through its second generation, the GLS has been facelifted. Big news includes the adoption of Mercedes' most up to date nine-speed 9G-Tronic transmission on all models, bar the GLS63 AMG which retains the old seven-speeder. One engineer said this was because the old 'box offers sportier and more 'emotional changes'. But you wonder if the combination of the nine-speeder with the monstrous twin-turbo 5.5-litre V8's 585hp and 560lb ft torque peak would end in tears and a casing full of shrapnel.
Externally, you'd be hard pressed to pick out the stylistic changes, save a new twin power domed bonnet. There's also a pair of new LED headlamps and new tailpipes, but that's about it.
The more interesting changes are hidden from view. We've already mentioned the GLS63 AMG, now boosted by 28hp. But there's also now a 3.0-litre twin-turbo petrol, badged GLS400 that delivers a decent 333hp and 354lb ft. The GLS500 carries over its twin-turbo 4.7-litre V8 with a more generous 455hp and 516lb ft, boasting an impressive (for a 2.5-tonne petrol powered SUV) 28mpg.
For those who live in the countryside, pay attention now because the biggest Merc SUV has some serious off-road potential. Tick the option box for the Off-Road Engineering Pack and your GLS will come with a centre diff lock and low-range gearbox, plus a special off-road mode that jacks up the suspension to give a ground clearance of 306mm.
Depth of ability
With just a hint of the off-roading ability possessed by the mighty G-Wagen it all sounds impressive. Mercedes claims the GLS, as well as boosted off-road potential, can now wade up to depths of 600mm. That sounds decent, until you discover the Range Rover, without any added extras, will happily potter along submerged up to 900mm.
It's the Range Rover that draws constant comparison the more time you spend with the GLS. It is, after all, the SUV even those who don't like the breed can love. With the new name, Mercedes wants to narrow the gap between the GLS and its more luxurious rivals, even claiming its new car is more of a high-riding S-Class than a typical SUV.
Setting off in the diesel, the hushed 3.0-litre makes a decent stab of things. Off the line it takes 7.8 seconds to hit 62mph and feels brisk enough to not be a chore. Ride comfort is tricky to judge on the Austrian roads we're driving, but on the small amount of dirt roads we encounter the revised Airmatic suspension soaks up even the worst ridges. Those S-Class comparisons might be valid after all.
Thread the GLS through a busy ski town and you'll soon discover the other advantage of the GLS compared to the Rangie. Despite measuring in at a mighty 5.2 metres long the biggest Merc SUV is actually 106mm narrower than the big Brit. OK, 2,114mm (with mirrors) still isn't going to trouble any Kei cars, but for anyone who has to regularly squeeze through width restrictors, what you'll save on wheel repairs and new tyres will probably buy you a week away somewhere warm.
Since we're high in the Austrian Alps, it would be rude not to sample the SUV in the snow. This time we try a GLS400, on a snowy mountain pass with the Off-Road Pack. It's here the benefits of the Mercedes 4Matic drivetrain and new hardware can be felt and the added stability and traction in deep snow is close to astonishing.
Unfortunately, those hoping to unleash their inner Vatanen will be disappointed. Even with ESP disabled (it soon kicks back in) slip angles are limited. Instead, you just have to relish the surprising traction that, at one point, drags all 2.5 tonnes of GLS off a deep snowy bank, avoiding a nasty brush with the rocky scenery.
The twin-turbo 3.0-litre petrol V6 is a pleasant enough match for the GLS but, even if we had the option of it in the UK, it's not quite quick enough to justify over the diesel, despite posting a 6.6-second 0-62mph time. The V8 GLS 500 is - surprise, surprise - substantially better, both off the line (5.3 seconds to 62mph) and when you want an effective mid-range overtake. It makes for a very tempting package, if perhaps a little bit too quiet and cultured for people like us. Obviously we're itching to try the AMG version after this taster...
So would you have one over a Range Rover? Well, not to get all What Car? on you, but the big Mercedes is actually a genuine seven-seater and therefore offers a significant selling point over even the occasional seven-seat Range Rover Sport. As such it's really the Audi Q7 and Volvo XC90 you need to be comparing it against.
Despite being more expensive than both of those it's hard not to resist the Merc's more rugged charms and it's a better drive than the Volvo. Being able to pull 3,500kg is also commendable. More impressive, though, is fold down the third row of seats and you can carry an incredible 815kg, meaning it will cope with whatever you can throw at it. We're still not sure if it's completely PH-worthy, not until we've tried the AMG version. For now GLS will just have to settle for being the ultimate family bus.
Although, didn't they also used to be bigger?
Official promo vid here.
MERCEDES-BENZ GLS350d 4MATIC AMG LINE
Engine: 2,987cc V6 turbocharged, diesel
Transmission: 9-speed automatic, four-wheel drive
Power (hp): 258@3,400rpm
Torque (lb ft): 457@1,600-2,400rpm
Top speed: 138mph
MPG: 37.2mpg (NEDC combined)