Parkers overall rating: 3.1 out of 5 3.1
  • Not the most comprehensive engine range
  • Diesel-only initially, mild-hybrid petrols came later
  • No plug-in versions available… Yet

There’s a limited range of three engines to choose from, each tailored to suit the preferences of different types of buyers.

Only one version of the GLS was initially available in the UK. Called the Mercedes-Benz GLS 400 d, it features a stout 2.9-litre diesel that produces enormous pulling power – or torque – channelled to all four wheels via a nine-speed automatic and Mercedes’ 4Matic all-wheel-drive system.

Grey 2020 Mercedes-Benz GLS 400 d front three-quarter driving

Despite being the entry-level model within the range it delivers more than ample performance, decent real-world fuel economy and impressive refinement – the engine’s hardly audible even when pushing very hard, and few mechanical vibrations make their way to the car’s interior.

When you need to drive sedately, such as around urban environments, the 400 d is pleasingly docile and easy to manoeuvre gently thanks it its linear power delivery and an automatic transmission that flits between ratios in a barely perceptable manner.

If the Mercedes GLS could be remotely described as sensible, then the diesel would epitomise it, but luxury SUV buyers are rarely pragmatic, hence the existence of the petrol versions.

White 2021 Mercedes-AMG GLS 63 front three-quarter driving

We are yet to drive either the AMG GLS 63 or Maybach GLS 600, which share the same basic 4.0-litre petrol V8 tuned for different power delivery characteristics, but on paper each delivers monstrous performance and thirst for super unleaded. That despite each being fitted with a 22hp mild-hybrid system.

This is almost besides the point, though: they on sale because they allow buyers to project something about their status and what’s important to them. Until there’s a switch to would-be customers wanting to promote their environmental awareness a plug-in hybrid (PHEV) or fully electric GLS won’t be available.

How does the Mercedes-Benz GLS drive?

  • Focus on comfort over anything else
  • Not particularly agile
  • Clever suspension options available abroad

The GLS proves a relaxing car to drive thanks to new underpinnings that are designed to boost comfort. It comes with adaptive air suspension as standard, too, which adjusts its characteristics on the fly to suit the road conditions – and also keeps the car level, regardless of load.

It floats over smooth surfaces and adjusts itself impressively well – even Sport mode offers a decent degree of comfort. Leave the car in Comfort and it can get a bit wallowy over undulating road surfaces. It can sometimes thud into bigger holes and, with such large wheel sizes available (up to 23 inches), this feeling is heightened. The Range Rover and BMW X7 both do a better job here.

The GLS even handles quite well for such a large beast. On a twisty road it’s best in Sport mode to keep the large body in control, but when fitted with the e-Active suspension system, there’s a function called Curve to actively tilt the car into a corner to reduce body roll. It takes a little getting used to, but it doesn’t leave you rolling around in the car.

Mercedes-Benz GLS SUV front wheel detail

There’s not a huge amount of feedback in the steering wheel, but you wouldn’t really expect there to be. It’s easy to drive the GLS though, which will be far more of a priority than how sporty it feels.

Impressive off-road ability

While it’s unlikely that any GLS will ever venture far off the beaten path, Mercedes has served up an upgrade that boosts the big SUV’s off-road capabilities. It’s called the Off Road package, which costs £1,495, and includes upgrades such as a low-range crawler gear, hill descent control and off-road calibration for the ABS.

Even without this kit fitted, the GLS is more than capable of tackling some tricky terrain thanks to adjustable air suspension.

Two off-road driving modes are available via the Dynamic Select system, adjusting the car’s systems to most effectively make its way over tough surfaces. It’s more than a match for Land Rover’s selection of cars, which is impressive in itself.

Grey 2020 Mercedes-Benz GLS 400 d driving through muddy water