Ever since Mercedes-Benz bestowed the GLS moniker to its largest SUV, it’s been billing it as the “S-Class of SUVs” – even though the car was really just a bigger GLE with an extra row of seats. Now, however, Stuttgart has finally put its money where its mouth is by giving the new X167 model more of everything, in an effort to fend off advancing competition like the new BMW X7.

Not least of its efforts is the car’s impressive girth. Measuring 5,207 mm long and 1,956 mm wide, the new GLS is 77 mm longer and 22 mm wider than before, while its 3,135 mm wheelbase is 60 mm longer. To put that into perspective, that’s just 39 mm shorter than a long-wheelbase S-Class and 57 mm wider.

Masking that increase in dimensions is a more athletic design that bears more than a passing resemblance to the latest GLE, complete with the upright octagonal grille that is becoming a hallmark of Mercedes SUVs. Marking its status as a true range-topping model, the car comes as standard with Multibeam LED headlights with three daytime running light sections (as per the S-Class) and a whopping 112 diodes on each side.

Along the side, there are squared-off wheel arches and softer, calmer surfacing than before, topped off by the powerful rear haunches that flow into the tail lights. Speaking of which, the broad two-piece LED lamps get three-dimensional blocks which are again reminiscent of the GLE, and they’re joined by a full-width chrome strip. Despite the massive size, the GLS has a drag coefficient of just 0.32, down from 0.35.

The dashboard is also shared with the GLE, with the usual Mercedes flatscreen display panel – with twin 12.3-inch displays as standard – mounted on a distinctive vent-like support, plus a tall centre console with integrated grab handles. As on the GLE, the GLS comes with the Mercedes-Benz User Experience (MBUX) infotainment system with an optional Interior Assistant gesture control system.

It’s at the rear, however, where the GLS really earns its lofty billing. All seven seats are power-adjustable as standard, and you can also spec the car with six seats – replete with armrests for the second row – for even greater luxury. These second-row seats, which offer 87 mm more legroom than before when placed in their rearmost positions, can be outfitted with heating, ventilation and massage functions.

Those passengers also get access to an extended centre console with cupholders, a wireless smartphone charging pad and additional USB ports so that your kids’ phones will never run out of battery. There’s even an optional five-zone (!) climate control system with a dedicated heater and air-conditioner for the third row – which, by the way, is full-sized and can seat people up to 194 cm in height.

Entertainment is provided by way of the optional MBUX Rear Seat Entertainment System, which consists of twin 11.6-inch touchscreens that can be used to watch movies, listen to music, use the integrated web browser or even view trip information. Another optional feature is a seven-inch Android tablet as part of the Rear Comfort package Plus, which can be used to control the infotainment, seats and climate control.

The seats can be folded flat using buttons in the boot, and there’s also a button to stow all seats simultaneously. Do that and cargo capacity swells to a humongous 2,400 litres, and the loading of larger, heavier items can be made easier by lowering the standard Airmatic air suspension by approximately 50 mm.

Motivation comes from a range of petrol and diesel engines, the former with an EQ Boost 48-volt mild hybrid system that adds 22 hp and 250 Nm of boost. From launch, the GLS 450 will be offered with an M256 3.0 litre twin-turbocharged straight-six producing 367 hp and 500 Nm of torque, while a GLS 580 will arrive shortly after. This debuts a new mild hybrid version of the M176 4.0 litre biturbo V8, producing 489 hp and 700 Nm.

On the oil burning side is the OM656 3.0 litre turbo straight-six in two variations – a GLS 350 d with 286 hp and 600 Nm and a GLS 400 d with 330 hp and 700 Nm on tap. Both versions come with a selective catalytic reduction (SCR) converter with an ammonia slip catalyst (ASC) for more efficient use of AdBlue liquid.

All models are fitted with a nine-speed 9G-Tronic automatic transmission as well as a 4Matic all-wheel drive system – this can send up to 100% of torque to each axle and induce oversteer or understeer on demand for improved safety and agility. A new off-road transfer case with a low-range gearbox is available.

The air-sprung chassis comes with Adaptive Damping System Plus as standard, but buyers can specify a 48-volt E-Active Body Control system which can individually control the spring and damper rates on each wheel, providing improved comfort and off-road performance. This system enables the car to lean into corners and even rock itself free when stuck in sand.

Another new feature is the Carwash function that will enable easier entrances into carwashes. In this mode, the suspension moves into the highest position to reduce track width, while the mirrors fold, the windows and sunroof close, the 360-degree camera system is switched on and the rain-sensing wipers are turned off. The climate control also enters into air recirculation mode.

As expected, safety kit is vast and includes the full complement of semi-autonomous driving features. These include Distronic adaptive cruise control with the new Active Stop-and-Go Assist that will automatically keep the car in its lane at speeds of up to 60 km/h – mirroring the Level 3 self-driving functionality on the new Audi A8. Trailer Manoeuvring Assist is also offered as an option in Europe.

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