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2020 Mercedes-Benz GLS 400d review

By Cameron Kirby, 30 Jan 2020 Reviews

2020 Mercedes-Benz GLS 400d review

With more acreage than a country estate, the biggest Benz SUV makes a commanding statement

Overall Rating

5 0 5

Plus & Minus

  1. PlusPlush ride, composed dynamics, cavernous space, smooth and gutsy engine

  2. Minus Entry price premium compared to rivals, cost of some options

The Wheels Verdict: The GLS’s only major downfall is the price premium Mercedes demands compared to key German rivals. However, judged on its merits, the big Benz delivers, with real presence and almost unparalleled cabin space and comfort. A gutsy diesel engine, paired with refined ride and dynamics make it a compelling all-rounder.

What is the Mercedes-Benz GLS 400d?

Now in its third generation, the Mercedes-Benz GLS is the biggest SUV in the German brand’s range. It majors on luxurious practicality, with two variants on offer powered by a pair of straight-six turbocharged engines. The higher-end AMG and Maybach versions will arrive later in the year.

Why we’re testing it

Australia’s appetite for luxury behemoths of this ilk is only growing. BMW’s X7 and Audi’s Q8 offer two distinct takes on the genre – the former offers copious space, while the latter focuses more on driving dynamics. The GLS is more expensive than both, so we need to find out if it can beat its specialist rivals by doing enough to offer the best of both worlds.


Segment creep is an automotive phenomenon where cars grow by a few centimetres each generation. These are often nominal increases at the time, but over the decades it results in situations like how the current 3 Series appears bloated and oversized if put side-by-side with an original E21.

Mercedes-Benz has taken this to the extreme with the GLS, stretching by 77mm compared to the previous generation, bringing its total length to 5207mm. Of that extra length, 60mm has been added directly between the wheels, boosting the wheelbase to 3135mm.

Why has Mercedes done this? It’s all in an effort to make the GLS one of the most practical vehicles for moving a large number of people (and their luggage) this side of a commercial vehicle.

Read next: Australia's best value large SUV 7-seat winner

Powering the GLS is a choice of one of two 3.0-litre straight-six turbocharged engines, which send power to all four wheels via a nine-speed automatic transmission. The GLS 450 starts the two variant range at $146,500, powered by an ‘M256’ petrol engine with EQ boost (fancy speak for a mild-hybrid system) sending 270kW/500Nm to the treads.

However, it’s the $153,300 GLS 400d that we have on test, powered by the ‘OM656’ diesel, with claimed outputs of 243kW and 700Nm – sizeable increases of 53kW and 80Nm compared to the second-gen GLS 350d it replaces.

This is expected to be the more popular variant, and acceleration is claimed to be a crisp 6.3 seconds to 100km/h – impressive considering the nearly 2.5 tonne heft of the vehicle.

Behind the wheel it’d be easy to forget you were driving a diesel engine, with nary a hint at any of the old oil-burner clichés present. It’s just the lowly redline that gives the game away, and that prodigious low-end torque. The nine-speed gearbox shuffles between gears subtly, without constantly searching for the right ratio when you lay into the throttle

Fuel economy is a claimed 7.7L/100km, which combined with a 90 litre fuel tank, means the GLS 400d’s cruising distance stretches well into the 1000km range.

AMG Line styling is standard in Australia. This is the first Merc which can be fitted with 23-inch wheels from the factory; our test vehicle came with 22-inch rims as part of a $2500 night package styling option, wrapped in meaty Continental Premium Contact 6 rubber – 285/45/22 at the front, and 325/40/22 at the rear.

Read next: 2019 BMW X7 vs Mercedes GLS on paper

Air suspension is standard, with Merc engineers reworking the front axle design in an effort to reduce tyre noise and vibrations. As a result, the ride is plush and cosseting, with impressive body control. Damping is well sorted, with the GLS regaining composure quickly following large bumps.

This is not to the detriment of dynamic ability either, with the GLS able to be hustled at a speed that defies its imposing physical stature. Describing it as agile would be a stretch, particularly on tighter mountain roads, but on medium to large radius bends the GLS has confident turn in, and planted mid-corner grip. In sport mode the car becomes more composed dynamically, without becoming overly stiff.

Mercedes’ crazy E-Active Body Control system is available if you want to ratchet comfort levels up further, for an eye watering $13,000, but how much are you willing to pay to essentially eliminate speed bumps from existence?

The cabin is hushed at cruising speeds, with impressive refinement keeping noise intrusion from wind and road at a minimum.

The dimensional nip and tuck hasn’t been in vain, with the GLS offering supreme space inside for both animate and inanimate cargo. Second row seats can slide fore and aft, with up to 87mm of leg room offered, which is extremely generous.

Mercedes claims people up to 6ft4 can feel comfortable in the third row of seating. While we didn’t wedge someone that large into the space, your 6ft1 writer clambered in and out with relative ease, and didn’t feel cramped in the space, comparing it to many mid-size SUV second row seats.

Read next: Mercedes-Maybach raises the luxe SUV stakes 

If you want to understand the lengths Mercedes has gone to expand the GLS, even the sunroof is 50 percent larger than the previous generation.

Boot space is, frankly, vast. With all three rows of seating raised there’s 355 litres of luggage space, growing to 890 litres with just two rows being used. These are increases of 60 and 210 litres respectively compared to the previous generation GLS. With both second and third row seats folded flat, the GLS offers 2400 litres of luggage space, with 2.2 metres of useable length.

A switch is easily accessible at the boot which lowers the rear of the car, and each seat can be electronically raised or lowered individually. The spare wheel in the boot can be accessed even with all three rows of seats being used.

Despite its almost six-metre length, the big Benz isn’t unwieldy, with an admirable 12.5-metre turning circle, and enough parking cameras and sensors to land a lunar module.

Heated and cooled seats, with hot stone massage function, are standard up front, while the powered seats now have increased adjustability. Six USB-C ports are offered to rear seat occupants, in addition to the four cupholders and two bottle holders. Child seat top tether attachments are available for second and third row seats; while five-zone climate control is standard with no shortage of air vents offered in each row.

The driver is treated to a massive head-up display that feels like something ripped straight from a science-fiction fighter jet. All the information you could desire is offered up, without having to take your eyes off the road. If you do lower your gaze, information is displayed on the dual 12.3-inch displays which turn the central touchschreen and driver instruments into one continuous panel. These are powered by Mercedes’ MBUX system, which includes Apple CarPlay and Android Auto as standard.

Read next: WhichCar should I buy instead of a large SUV?

Stuttgart’s entire safety suite is offered as standard, while augmented reality sat-nav is part of an $800 option. This system, which is relatively new to Australia, is best suited to situations where you are driving in unfamiliar territory.

The GLS has a towing rating of 3500kg, but you’ll need to fit the optional $1900 towbar package before you hitch a wagon to the rear. If you are a proper off-roading masochist, you can also tick the box for the $3500 off-road engineering package catering to those specific needs, which includes a low-speed transfer box among its goodies.

These sorts of options could raise the price of the GLS even further above its rivals, which sit in the lower half of the $100,000 bracket. This is the Mercedes’ only real downfall, with premium pricing compared to rivals. But for the way it pairs practicality with luxury and driving dynamics, we’d argue the price is worth it if you are in the market.

Read next: Top-spec family seven seat SUVs compared 

The rivals

BMW X7, Audi Q8, maybe a bus?

Specs and price

Model: Mercedes-Benz GLS 400d

Engine: 2925cc straight-six, dohc, 24v, turbo diesel

Power: 243kW @ 3600-4000rpm

Torque: 700Nm @ 1200-3000rpm

Transmission: 9-speed automatic

Weight: 2490kg

0-100km/h: 6.3sec

Economy: 7.7L/100km

Price: $153,300 ($158,700 as tested)

On sale: Now