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Can Mercedes’ third-generation GLS behemoth justify its claim to be the ‘S-Class of SUVs’?

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The Mercedes-Benz GLS, which is now entering its third full model cycle, has become something of a strange idol for those who believe, absolutely and unquestionably, that bigger must necessarily mean better when it comes to luxury cars.

It hasn’t always been known by that initialism. The first version, which stretched the Mercedes ML-Class’s underpinnings to suit a proper adult-sized seven-seat SUV application, was called the Mercedes GL (2006-2012) when it came along in 2007 and helped provide the production volume to establish Mercedes’ US factory in Alabama.

The GLS would be a very odd flagship SUV for Mercedes, but the fact is that it isn’t anything of the kind any more. It has been so plainly usurped by the latest G-Class, which has all the sense of identity and authenticity that the GLS lacks.

But now that first mission has been achieved, and with so many ways to spend a six-figure sum on a leather-lined, exotically positioned luxury 4x4 today that simply didn’t exist 13 years ago (not to mention a much improved Mercedes G-Class sibling rival with which to compete), does Mercedes need to redefine this car’s brief and positioning? Does the BMW X7 represent a direct challenge to which Mercedes must be seen to react? Which way does the biggest Mercedes SUV of them all now turn to ensure its continued existence – or does it simply plough steadily straight on in global market conditions that supposedly remain favourable to all cars of its ilk?

All these questions and more must have concerned Mercedes’ product planners during the initial design and conception of the X167- generation GLS, which undergoes this week’s road test in what is effectively the only engine and trim-level derivative form in which it’s offered to UK buyers: as the six-cylinder diesel GLS 400d.

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The firm describes the new GLS as more evolutionary than revolutionary, claiming it simply offers “more of the same: more space, more comfort, more luxury”. Stand by to find out, then, if even more really does mean more in this particular case.

The GLS line-up at a glance

Although the GLS is available with a much wider range of six- and eight-cylinder petrol and diesel engines in other markets, the 400d is the sole choice for the UK. AMG Line is the entry-level trim offering, with Premium, Premium Plus and Premium Plus Executive add-on packs optionally available.

Mercedes-AMG has recently unveiled the monstrous GLS 63, whose 4.0-litre V8 develops 603bhp and 627lb ft with assistance from a 48V mild-hybrid system. This model will arrive towards the end of spring.

Price £75,040 Power 326bhp Torque 516lb ft 0-60mph 6.5sec 30-70mph in fourth 6.9sec Fuel economy 30.0mpg CO2 emissions 213g/km 70-0mph 45.5m


Mercedes-Benz GLS 2020 road test review - hero side

It’s fitting that the Mercedes GLS is assembled in the spiritual homeland of big-boned SUVs; specifically, at Mercedes’ Tuscaloosa plant in Vance, Alabama. And this widely redeveloped model does cast quite the shadow, being 77mm longer and 22mm wider than the previous GLS and with a footprint comfortably larger than that of its closest rivals, the BMW X7 and Range Rover.

Indeed, it dwarfs conventionally big cars such as the Volvo XC90 and has a wheelbase 100mm longer than that of even the long-wheelbase Mercedes S-Class. Is that too big – at least, for UK roads? We’ll see, but to go bigger in Europe, you would need the Rolls-Royce Cullinan.

It will be a modest step to get into the GLS for most people, and a big one for some – particularly if the air suspension is at its highest setting – so these running board steps come in very handy. They look the part on the car, too.

As is commonplace for models that could more accurately be described as high-riding limousines than off-road vehicles, the GLS’s construction is more S-Class than Mercedes-Benz G-Class. Each axle uses pneumatic springs and, although those springs are controlled with double-wishbone suspension at the front axle, the rear uses a multi-link arrangement. It’s all attached to Mercedes’ Modular High Architecture, which is largely the same as the Modular Rear Architecture used by the S-Class, Mercedes-Benz E-Class and Mercedes-Benz C-Class saloons.

This hardware lays the ground for cutting-edge autonomous driving features and is said to weigh less – at 2415kg, the claimed weight for this GLS 400d 4Matic makes it 40kg lighter than the car it replaces. The 400d will remain the only powertrain available to UK buyers until the Mercedes-AMG 63 (twin-turbocharged V8) arrives later this year.

The 400d uses the same 2925cc ‘stepped-bowl’ straight-six twin-turbo diesel available elsewhere in the Mercedes range – and highly rated it is, too, for its response and refinement. Mated to Mercedes’ nine-speed gearbox, it delivers 326bhp and a robust 516lb ft and does so with new-found versatility. Whereas the old GLS powertrains used a fixed 50:50 torque split, the new powertrain is variable, defaulting to rear-wheel drive for sweeter drivability on the road but able to shift half the torque forward via its centre differential.

The two most notable option packs are the Off-road Engineering Package, which is fitted to our test car, and E-Active Body Control, which uses stereoscopic cameras (that is, two feeds rather than one) to scan the road ahead and prime the dampers – and that, for some reason, isn’t available in the UK. The Off-road Engineering Package adds a low-range transmission, off-road ABS and the ability to lock the driveline’s central coupling.


Mercedes-Benz GLS 2020 road test review - cabin

The Mercedes GLS' cabin is a likeable environment, but doesn’t feel quite as rich or special as the ‘Mercedes-Benz S-Class of SUVs’ strapline suggests it should. There’s much that gives an impression of the smaller Mercedes GLE, only scaled up in size, which feels like a cop-out in a flagship luxury SUV. Cars like this deserve a more bespoke ambience.

Those with a keen eye will note the array of squared-off air vents set in an attractive brushed aluminium dashboard fascia, while the slender grab handles that protrude from the centre console have also been carried over from the GLE. All the switchgear is largely familiar, as are the shapes and locations of numerous storage solutions dotted around the front of the cabin. But as familiar as the GLS’s cabin is, the same argument applies to the likes of the BMW X5 and BMW X7.

GLS features sizeable grab handles but, because this is the self-styled ‘S-Class of SUVs’, they’re trimmed in Artico ‘leather’ and have aluminium inserts.

The twin screens of the latest MBUX infotainment suite dominate the dashtop and the Mercedes feels like the more technologically sophisticated seven-seat SUV when compared with its closest German opponents. As a bona fide seven-seat SUV, however, the X7 outshines the GLS for three-row practicality. Both have cavernous second rows (the Mercedes has up to 850mm of leg room and 990mm of head room), but the X7 pips it for third-row space. We have yet to take a tape measure to the BMW, but previous experience confirms adult passengers can fit in the rearmost seats in impressive comfort. In the GLS, these seats are best left for larger children.

Boot space ranges from 470 litres with the rearmost seats in place to a gargantuan 2400 litres with two rows of seats folded dead flat.

Mercedes-Benz GLS infotainment and sat-nav

Mercedes’ expansive MBUX infotainment system continues to impress, with pin-sharp graphics and intuitive menus, even if the rotary controller found in the BMW X7 still beats the trackpad used here for making quick, precise commands on the fly.

The two 12.3in displays nevertheless convey the feeling of technological superiority that Mercedes will have intended and, alongside the system’s capacity for voice and gesture control, the central display is touch sensitive, and so your angles of attack are many. Apple CarPlay and Android Auto compatibility come as standard, with no associated subscription fee.

Premium Plus Executive trim extends the technology to the second row, adding wireless phone chargers, extra USB connections (for 11 in total) and 7.0in tablets, which can themselves be upgraded to 11.6in touchscreens with the MBUX Rear Seat Entertainment System.


In many facets of the driving experience, the Mercedes GLS’s considerable size and its bulk are concealed about as effectively as a hippopotamus might be by an acacia tree – but this one isn’t one of them. A weight on our scales of 2.6 tonnes may be a lot for any engine, but GLS’s 2.9-litre twin-turbo diesel straight six develops more than 200lb ft for every tonne of that kerb weight – and makes that torque available from just 1200rpm.

The upshot is that the GLS 400d is at once quicker and more drivable than you’d perhaps expect – as well as a fair bit more smooth and refined. It has the dampened-down initial throttle response that you’d want in a big, heavy car that’s likely to be pressed into service for towing and occasional off-roading, but it isn’t at all reluctant to get moving once it’s rolling. When it’s really spurred on, it’ll pass 60mph from rest in just 6.5sec, and get from 30-70mph in just 6.0sec; which is about as quick as a Ford Fiesta ST.

Although I was largely impressed by the Merc’s engine, its stop/start system could be smarter. It’d cough back into life a bit too vigorously and could at times prematurely cut the engine when rolling to a stop

But more impressive still than that outright pace is how pleasantly, quietly and obediently the Mercedes GLS’s engine and transmission go about day-to-day business. The diesel straight six feels remote and well-mannered at both low and high crank speeds, and is powerfully responsive across its operating range. There is more noise and mechanical industry about its character above 3500rpm than below that threshold, but never a hint of harshness – and the car’s nine-speed torque-converter gearbox has a knack for selecting the right gear at the right time when you’re rowing the car onwards at the briskish but unhurried pace that its size seems to freely permit.

To drive the car off road is to appreciate the inherent advantage of such carefully tuned pedal response, because momentum becomes very easy to closely manage over mud and when climbing and descending. The brake pedal tuning is also very progressive, making it easy to stop smoothly wherever you are – although also making for an awful lot of travel to push through, and a slightly disconcerting overall feel to the pedal, during hard or sudden stops on the road. That all 2.6 tonnes of the car could be stopped from 70mph in less than 46 metres – and in damp, chilly conditions – suggests there’s nothing wrong with outright stopping power, however.


Mercedes-Benz GLS 2020 road test review - cornering front

While there’s no escaping its mass or girth, the Mercedes GLS doesn’t possess that supertanker-stranded-in-a-duck-pond feel you might expect on UK roads. Its lofty driving position is a key factor here, affording a commanding view that makes the task of placing and then keeping its enormous size within the confines of your lane reasonably easy most of the time – provided said lane is wide enough in the first place.

Around town, this elevated visibility is very useful indeed. It does little to make the GLS any more manoeuvrable in tight car parks or in narrow side streets, mind you – where you really do feel the car’s size, and where, at times, you can’t help wishing Mercedes had considered adding four-wheel steering. But aided by steering that, at 2.8 turns between locks, is not only sensibly geared and precise but also convivially light, the car’s reasonably tidy and responsive handling does at least make the process of navigating the GLS through traffic and around urban junctions a little easier than its sheer size might suggest it should be.

High-riding view makes road placement easier than its size might suggest, while cornering grip levels are commensurate with expectations of a heavyweight luxury SUV

Move up to open-road speeds, however, and while the process of flowing the GLS down a quick road remains reasonably intuitive, the car’s handling doesn’t quite mask its mass as effectively as it might. Steering response becomes notably more leisurely, while the amount of body roll that accompanies a more hurried style of driving begins to feel pronounced. Nevertheless, the steering’s linearity – as well as the subtle sense of elasticity that gradually builds as you wind on lock – ensures that there’s a reassuring sense of steadfast stability and predictability about the car’s limit-handling behaviour.

Grip levels are good if not infallible, and being roughly where you’d expect them to be in a modern 2.6-tonne luxury SUV. Push hard enough and it will be the GLS’s 285-section front tyres that relinquish their purchase first, allowing the chassis to gradually push into gentle understeer, at which point the car’s sympathetically tuned ESC system gracefully steps in to tidy things up so that, as often as not, you might not even notice the line you’ve just crossed.

Assisted driving notes

Mercedes remains in a strong position for the functionality and effective integration of its semi-autonomous driver assistance systems; and because the GLS comes in such a well-equipped specification, it gets the whole lot as standard.

The automatic lane-keeping system has a more guided feel than some, but still requires enough input from you to keep you engaged. Although it doesn’t always work well on single carriageways, it recognises lane markings on dual carriageways consistently – and usually even through roadworks – and its assistance feel can be turned up and down according to preference. The speed limit assist system generally recognises speed limits very consistently, too.

The intelligent cruise control is one clearly tuned primarily for the North American market, so it doesn’t guard against undertaking a slower-moving car; but in busy traffic, that can allow for smoother progress.

Comfort and isolation

In light of all the Mercedes S-Class limousine references that Mercedes pretty freely makes about this car, you’d expect its engineers to have made damn sure that it performs exceptionally with regards to ride comfort. It was with some disappointment, then, that our testers noted the manner in which the GLS addresses typical British A- and B-road surfaces.

Uneven stretches of country road highlight a tendency for the GLS body control to succumb to pronounced side-to-side jostling, while the car’s secondary ride seems happy to fuss and amplify some of the numerous ruts and edges that it deals with – most noticeably at town speeds. A degree of ride sophistication might well have been sacrificed in order to beef up the Merc’s off-road worthiness, but the similarly capable BMW X7 does notably better to isolate its occupants – and it’s not the only GLS rival you could claim that about. The fact the BMW comes as standard with 21in wheels, as opposed to the larger 22s on the Mercedes, could well be a contributing factor.

Over more uniform undulations, the GLS’s primary ride is at least defined by a likeable pillowy feel. The way its Airmatic suspension works to check vertical movement doesn’t make for as much outright high-speed body control as you might like, which is more than likely a product of its immense weight; but remembering that this is a luxury car, that is at least forgivable.

On smoother motorway surfaces, cabin serenity is good. At a sustained 70mph, our microphone returned a reading of just 62dB – one decibel quieter, believe it or not, than the S350 Bluetec we road tested back in 2013.


Mercedes-Benz GLS 2020 road test review - hero front

At first glance you might just conclude the £75,040 Mercedes GLS 400d somehow offers, as the saying goes, quite a lot of car for the money. The equipment list does little to dispel this notion, because even heated second-row seats and a head-up display come as standard. However, to benefit from the car’s autonomous tech, you will need to upgrade to Premium Plus trim level, which includes massage seats but raises the buy-in to more than £83,000.

The GLS is, however, forecast to hold its value better than its BMW X7 and Range Rover rivals, retaining 45% of its purchase price after three years and 36,000 miles compared with 42% for the similarly priced BMW X7 30d M Sport and 43% for the more expensive Range Rover SDV6 Vogue. It’s a marginal advantage only, on what remain pretty conspicuously expensive cars to own.

The Mercedes manages to narrowly outshine the Range Rover and BMW X7 for residual values, according to our forecast

In terms of outright usability, the Mercedes also scores well elsewhere. A test average of 30mpg is encouraging for a car of this size, performance and weight and, with a 90-litre fuel tank, makes for a real-world driving range of almost 600 miles. On the motorway, expect that to climb to more than 750 miles as economy approaches 40mpg.

Meanwhile, towing capacity is in line with diesel rivals at 3500kg for a braked trailer. Note, however, that this falls to 3300kg if you specify the Offroad Engineering Package.



Mercedes-Benz GLS 2020 road test review - static

In this almost shamelessly aggrandised class, recreating the superiority of the Mercedes S-Class was always going to pose an interesting challenge.

Just as hot hatch virtues rarely translate into their higher-riding crossover counterparts, the greatest attribute Mercedes’ famous limousine possesses – its sublime ride quality – appears to have been lost during the journey upwards. That the latest Mercedes GLS has not received an interior to truly dazzle its occupants seals its fate as an outwardly impressive but ultimately unremarkable addition to the Mercedes line-up.

It has much to commend it but not enough to be an S-Class of SUVs

None of which is to say that this car won’t enrich the lives of owners. Its straight-six diesel powertrain is superb and the cabin is comfortable and spacious enough for the longest of journeys, where the car’s enviable aural refinement comes to the fore. The high driving position will also give GLS drivers exactly what they’re looking for.

In this sense, and considering its passable off-road ability, the GLS has surely done enough to cement sales success. Just don’t expect rivals to lose much sleep, as they most certainly do with the S-Class.

Matt Saunders

Matt Saunders Autocar
Title: Road test editor

As Autocar’s chief car tester and reviewer, it’s Matt’s job to ensure the quality, objectivity, relevance and rigour of the entirety of Autocar’s reviews output, as well contributing a great many detailed road tests, group tests and drive reviews himself.

Matt has been an Autocar staffer since the autumn of 2003, and has been lucky enough to work alongside some of the magazine’s best-known writers and contributors over that time. He served as staff writer, features editor, assistant editor and digital editor, before joining the road test desk in 2011.

Since then he’s driven, measured, lap-timed, figured, and reported on cars as varied as the Bugatti Veyron, Rolls-Royce PhantomTesla RoadsterAriel Hipercar, Tata Nano, McLaren SennaRenault Twizy and Toyota Mirai. Among his wider personal highlights of the job have been covering Sebastien Loeb’s record-breaking run at Pikes Peak in 2013; doing 190mph on derestricted German autobahn in a Brabus Rocket; and driving McLaren’s legendary ‘XP5’ F1 prototype. His own car is a trusty Mazda CX-5.

Mercedes-Benz GLS First drives