The biggest and fanciest Mercedes SUV just got bigger and fancier. The new 6- or 7-seat GLS is a colossal luxury tank with whopping big touchscreens and tablets everywhere, five-zone climate control, a learning-capable AI voice assistant, and electric assist for all engine variants.

The current model GLS is already just about unparkably enormous, but Mercedes has decided biggest is best, and extended the new model in all directions. Thus, it's 77 mm (3 in) longer and 22 mm (0.87 in) wider for 2020, with a 60 mm (2.4-in) longer wheelbase that helps free up a decent chunk of extra legroom in the second row.

That second row comes standard with a very European three seats, but can be optioned to have an American two luxury loungers instead. These can move a long way forward and fold to give folk easy access to the two seats in the back row.

As well as the two huge 12.3-inch screens accessible to the driver and front passenger, you can option the GLS with a Rear Seat Entertainment System that puts 11.6-inch touch screens in front of both row two passengers, and there's a further optional MBUX rear tablet that gives the kids the ability to drive the entertainment system from the very back row.

MBUX, of course, stands for the Mercedes-Benz User eXperience, the human-facing, pattern-learning brain of the car, which we've already seen on the gadget-packed GLE. This one does all the many and varied things that one can do, plus a few extra goodies. MBUX Interior Assistant, for example, puts a camera in the overhead console watching what the driver and front passenger's arms are doing. So when you hit the massage seat button, for example, the car knows whose buttocks to start kneading and whose to leave unmolested. There are also some simple hand gesture controls coming in, like moving your hand towards the interior mirror to turn on reading lights.

The driver, for their part, can also enjoy a new 720 x 240 pixel full color HUD while mashing away at pedals connected to a wide range of engine packages. The most interesting is a brand new GLS 580 4MATIC V8 petrol engine making 489 horsepower and 700 Nm (516 lb-ft) of torque, and returning highly impressive combined cycle efficiency figures around 10 l/100 km, or 23.5 mpg. Nice!

All petrol engines for the GLS come with an integrated starter/generator that gives them a touch of hybrid capability. EQ Boost can thus throw an extra 250 Nm (184 lb-ft) at the wheels whenever necessary for short bursts, helping with immediate acceleration, particularly when the gearbox is thinking about what to do next – and a regenerative braking system can grab back some of your kinetic energy to help you get going again, increasing the car's overall efficiency. There are also two diesel engine options, but those don't get any electric assistance.

In stop-start traffic or on the highway, the driver needn't mash pedals at all thanks to active stop/go assist and active distance assist – adaptive cruise control to you and I. Interestingly, though, the system takes speed limits into account for you and adjusts its speed accordingly, and if the car's cameras see a signposted speed limit that's at odds with what's in the GPS, it'll follow the signs preferentially.

Like the GLE, the GLS will ride on Airmatic suspension with adaptive damping that adjusts itself constantly to suit your driving and the road (or off-road, as if that's what you're buying a GLS for) conditions. That means, like the GLE, it'll lean slightly into turns to counteract centripetal forces and pretty much ruin the kids' games of squashing each other sideways in the corners. And its stereo cameras look ahead to prepare the suspension for bumps, dips, rocks and whatever else it might see coming.

It can also rock and rattle its way free if it gets bogged on a trail, and the GLS gets a new suspension feature in Carwash mode, which raises the car up high so the water can get into the undercarriage better, folds in the mirrors, closes windows and sunroofs, turns off the auto wipers and switches the air-con to recirculation mode.

The new GLS will be in American and Western European dealerships by the end of 2019. No pricing has been given as yet.

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