Our view:
When Mercedes tidied up its
range-wide badging in 2015, a few models got new nameplates. Some had bigger changes than others: the ML SUV, for example, became the GLE. The SLK roadster switched to SLC, a nameplate not seen in the Mercedes fold since 1981. And similarly, the GLK compact SUV - which was never sold in the UK -became the GLC... although we do get that the UK now.
Perhaps the least obvious alteration was to the largest Mercedes 4x4 of all, the GL, which simply had an S added to its name. Little else changed beyond that. The headlights and tail-lamp clusters were tweaked, as was the grille, while within it got an 'entirely new dashboard'. Which might as well read 'entirely lifted from the GLE', as you won't spot a huge amount of difference between the two.
This interior architecture is only an issue when you remember that the addition of the S to the name is supposed to allude to the S-Class, the GLS supposedly the SUV version of Mercedes' most luxurious vehicle. And while there's a lot in the cabin to reinforce that idea, it's not an S-Class on stilts. There's plenty to like - there's genuine space for seven adults, as the third row is big enough for grown humans, rather than just very young children. Those rear seats all fold electrically, so configuring the GLS's cabin is a doddle and also enormous fun, as you'll be needlessly flipping the chairs up and down several times, just to watch them performing their effortless contortions. The unerring quality of the leather and most of the fixtures and fittings is not to be questioned, either.
But that centre console with the eight-inch colour display looks, as we said earlier, like it was lifted straight from a GLE. That's no bad thing in itself, but if you're playing the S-Class card, then borrowing parts from lesser Mercs isn't the way to do it. Similarly, the instruments with the digital display sandwiched between is absolutely fine... in isolation. Yet if you've sat in an S-Class Coupe, with its sweeping dash, twin 12.3-inch TFT displays and ranks of buttons across the console, the GLS dashboard feels a tad underplayed.
Still, as it's a Mercedes interior then it's of a higher standard than most other cars out there. And all the space within is a direct corollary of the GLS's huge dimensions; it's the best part of 5.2 metres long and two metres wide... excluding the door mirrors. Some large, seven-seat SUVs have a knack of visually shrinking themselves from the outside, so they don't look hulking, but the GLS is not one of them. It's unapologetically dominant, and will tower over pretty much any other vehicle you care to park it beside.
Not that we dislike the looks, though. Either the AMG Line (from £69,860) or this higher-spec Designo Line - which commands a £8,235 price walk - suits the Mercedes' bluff physique well. Again, handsome though it is, for some its 'stretched GLE' appearance might not feel individual enough for something that's almost has a six-figure price tag, but we're inclined to give the GLS's design our seal of approval.
Ditto the driving experience, which is magnificent in the main. As a luxury all-rounder, the GLS is hard to beat. That 3.0-litre engine is a glory, replete with instantaneous torque, a dearth of turbo lag and discreet yet interesting vocals. Hooked up to the peachy 9G-Tronic automatic, the Mercedes has an abundance of go at all reasonable road speeds - for a 2,455kg off-roader with a 'mere' 258hp, it really does haul a lot harder than you might think.
And it's no lumbering mess in corners either, as despite its (largely) lovely ride quality, the body control on the Airmatic suspension with Adaptive Damping System is utterly remarkable for such a large luxury vehicle. Coupled to steering that is more communicative and direct than it really needs to be, it means you can flick the GLS 350 d into bends as if it were a much smaller vehicle. Further, threading it along narrow country lanes is no drama, despite its physical girth, and all this stress-relieving engineering is what makes travelling in the GLS such a sumptuous experience. Heaven knows how much the sound-deadening in this SUV weighs on its own, given you absolutely never hear the 295-section tyres rumbling along the tarmac, nor the wind flowing over the GLS's bulky frame.
There is one whinge, though. On anything but bobbly country B-roads, the Mercedes simply glides along on its Airmatic 'springs'. It therefore has the best ride quality, in that you never, ever notice it; instead, it smoothes away surface imperfections in towns, on fast A-roads and on dual carriageways/motorways like they simply don't exist. And then you get on a rutted British rural route, and something very strange happens. In a speed bracket from about 35-55mph, a weird lateral shimmy starts to make itself felt. It's as if a massive, invisible hand has reached down, grabbed hold of the GLS's metalwork and then given it a good shake from side to side - all without the chassis responding similarly. This quirk manifests itself in the heads of all occupants jiggling left to right over poor surfaces, as if all the people on-board had suddenly been turned into Bobblehead figurines. It's a most unusual and unpleasant sensation, which thankfully is only experienced in a handful of scenarios - but it's a shame it has to be experienced at all.
And while we're carping, the price is another sticking point. Mercedes will insist that the GLS has nothing to do with oik SUVs like the Audi Q7, BMW X5 and Volvo XC90. It will say the GLE is the 4x4 to take those on, while the GLS instead does battle with the larger pair of Range Rovers, the Bentley Bentayga and that forthcoming Rolls-Royce SUV.
All well and good, but that dashboard finish and the GLS 350 d's on-paper stats don't put it anywhere like in the Bentley's ballpark; it has about the comparable power and torque to a Q7 3.0 TDI, and the same sort of interior room as the Volvo. Yet it is clearly priced like an S-Class. There are just two engine options, although only one of them is sensible - that being this 3.0-litre diesel. Unless you happen to think a 585hp, 5.5-litre biturbo petrol V8 can in any way be deemed 'sensible' in a two-tonne, seven-seat SUV, in which case you'll be after the Mercedes-AMG GLS 63. And perhaps a straight-jacket, too.
But, even for the super-rich types who buy this sort of machine, does £82,920 as optioned (£1,695 Driving Assistance Package, £1,985 Off-Road Package, £950 Trailer Coupling Package and £195 black piano lacquer trim) really sound like a reasonable price for a car with its dashboard architecture rooted in the ML-Class era? One that is no quicker from 0-62mph than the GLC 250 d lower down the Mercedes SUV tree, a car which features the ageing 2.1-litre four-cylinder motor? Tricky questions to answer - although we don't doubt Mercedes will emphatically do so when the GLS is properly replaced with an all-new version in about three years' time. Expect it to have the glitzy TFT screens and a more bespoke console arrangement that should make it feel truly special.
That doesn't help the current model an awful lot, though, does it? Nevertheless, odd moments of bob-along ride aside, the rest of the GLS package remains deeply impressive. And if you do think it's a worthy rival to a Range Rover or a Bentayga, then the GLS's strengths are that it's a far rarer sight on UK roads than the former and a much classier thing to behold from the kerb (and significantly cheaper) than the latter. Finally, it proved genuinely economical while blatting around Norfolk on a family holiday - loaded up to the gunwales with all manner of clobber for a five-day trip, we covered 600 miles in the GLS 350 d and got 30mpg out of it in that time; not bad, considering that for 90 per cent of the trip it was wending around East Anglia's minuscule, sinuous roads and venturing into sleepy little conurbations where the average speeds were low. Its vast 100-litre fuel tank saw to it that we didn't need to go anywhere near a fuel station during the week. And if we'd needed it to, then the optional towbar fitted could have been hooked up to 3,500kg of braked trailer - that's impressive.
In summary, one letter added to its badge isn't enough to convince us that the GLS is the four-wheel-drive equivalent of an S-Class, but there's no doubt the 350 d is a very special machine regardless. If you've got the cash and you splash out on the massive Merc, you won't be disappointed with this superb seven-seat SUV.
