Mercedes-Benz Gls450 vs MG Im6

What's the difference?

The new GLS is everything you’d expect of a Mercedes-Benz with an S in its name. Luxury, performance, space, and in this case, thoughtful practicality. A super-capable, super-sized family truckster with the lot.

A super solid first outing from the IM brand. Don't let the pricing fool you, there is still bang for buck on offer in the IM6 Performance, even if it at times feels a bit too digital for my tastes.

Launched globally in mid-2019, Merc describes the GLS as the S-Class of SUVs, which is apt given its 5.2m length, 2.5-tonne mass, and ultra-premium specification.

As mentioned, the GLS is big; a step up from the already substantial model it replaces. Built with the US market in mind, in fact it’s produced in Tuscaloosa, Alabama, it’s more than five metres long, close to two metres wide, and over 1.8m tall. And there’s more than three metres between the axles, a 60mm wheelbase increase over the previous model.

And despite the size of the canvas, the Benz design team has managed to make the GLS look like a modern Merc. Signature elements include obvious ones like the slatted grille with a couple of three-pointed stars on the nose.

But there’s also, the carefully chiselled twin ‘power dome’ bonnet, scowling LED headlights and vents to aid front brake cooling and smooth aero performance around the front of the car.

The big beast’s off-road intent is highlighted by extensions around the wheelarches, with big optional 22-inch rims sitting underneath. The fact they look right-sized for the car speaks volumes about its scale.

The racy AMG Line package is standard, and a recess and pronounced character line, tightening the lower waistline is a familiar Merc treatment, plus alloy roof rails toughen the look while dialling up practicality.

The rear is relatively simple, borderline generic, with tapered tail-lights offering the only strong whiff of design personality. But believe it or not, thanks to careful detail sculpting of the body, and smoothing underneath the car it boasts a drag figure of Cd 0.32. Outstanding aero performance for a large SUV.

The driver and front passenger are presented with a sweeping dashboard dominated by twin 12.3-inch digital screens, one primarily covering the instruments, and the central screen managing the MBUX media system, including audio, nav, phone integration, car set-up, and more, plus ‘Hey Mercedes’ voice control.

The overall feel is simple, and restrained, yet massively confident, with a subtle colour palette, large squared-off elements defined by brushed metal finishes, and an obvious, intense attention to detail, from the haptic controls to the beautifully finished, multi-function steering wheel.

And the standard Burmester audio system includes a two-way in-car communication function that subtly amplifies the driver and front passenger’s voices for those in the third row, and vice versa. Sheer genius.

I feel almost mean saying this, because there will be plenty of people who like the way the IM6 looks, and I don’t want to rain on their parade. But… I’m not one of them.

It reminds me a bit of the pre-facelift Tesla Model Y, in that it’s largely feature-less and a bit blobby, and there’s not a sharp angle anywhere to be found on the thing. Premium to me means powerful and assured — picture just about any Audi — whereas I just find this a bit bland and soft.

Anyway, I do like the big alloys, the insulated glass roof and the light treatment front and rear.

And I like the cabin. The seats aren’t leather, but they’re super thick and comfortable, and there is a genuinely premium air in the cabin, helped by the acreage of screens and the quality elements, like the little door panels.

The doors unlatch electrically, matching the pop-out door handles outside, but they can be a bit fidgety. Someone from MG told me how they worked (you kind of cover the handle and let the door come to you) but I watched everyone else who tried to open them struggle. If you're at the point where you have to explain how a door handle works, you might have over-egged the pudding.

The second screen below the main one acts a bit like a mobile phone. You can alter your home screen widgets and access the main menu, even as Apple CarPlay is synched at the top. You’ll get used to it, I’m sure, but I found it to be a bit fidgety.

Actually it reminds me a little bit of the Lexus trackpad, or whatever that hateful system was called, where you controlled the main screen via a little mousepad thing, though happily it’s nowhere near as annoying as that was.

Space is obviously a critical factor here, and no surprise there’s copious amounts of it inside the GLS.

Front seat passengers enjoy plenty of breathing room, without feeling remote from one another, and there’s lots of storage in the shape of a large lidded box/armrest between the seats, a decent glove box, two big cupholders and jumbo door pockets with room for large bottles.

There’s one data-enabled USB port in the front, two charge-ports in the second row, and four in the third row. Shouldn’t be any complaints about powering mobiles, tablets or games.

The second row feels every millimetre the SUV limo. Simply getting in and out is made easier because an auto lowering function drops the car 25mm when one of the doors is opened.

I was able to sit behind the driver’s seat set for my 183cm position with heaps of head and legroom on offer. And there’s an extra 10cm of electrically adjustable travel to play with if those in the third row agree.

The fold-down centre armrest features a lidded storage tray and twin pop-out cupholders. There are netted pockets on the front seatbacks, and again, the door bins are big enough for large drink bottles.

Three adults across the rear is a breeze, there’s climate control ventilation, and a huge glass sunroof is standard. Rather than asking ‘Are we there yet?’ the kids will be disappointed when you arrive!

Then there’s what the Cleary family refers to as ‘the way back seat.’ A pair of third row seats for the lucky kids that get to inhabit their own little world. Getting in and out is relatively civilised thanks to electric slide and tilt for the second row seats, and space is generous. I could sit comfortably, so the kids will be all smiles.

With all seats upright cargo capacity is enough for a seven-person day trip (355L VDA). Press the button to fold the 50/50 split-fold third row down and your options expand substantially (890L). And with 40/20/40 split-folding second row lowered, transportation of a full, three-ring circus is on the cards (2400L). Overall, more space than the arch enemy BMW X7.

Plus, the ability to lower the car 50mm thanks to the standard air suspension makes life even easier. And one button lowers the second and third rows at the same time.

The spare is a collapsible space-saver, and towing capacity for a braked trailer is 3500kg, with a tow ball weight of up to 140kg. The ESP system also features a trailer stabilisation function that counters oscillation with “braking intervention.”

The IM6 measures 4904mm long, 1988mm wide and 1669mm tall, and it rides on a 2950mm wheelbase, with IM describing it as a "mid-large SUV", though I expect it will be classed as a medium SUV Australia.

That said, ICE and EV mid-size electric SUVs are not cut from the same cloth, with the latter making use of a flat floor to maximise space. And so it is with the IM6, where backseat room is pretty damn impressive. I’m 175cm, and I had no problem at all with legroom or headroom, plus the same plush seats from up there are in the back, too.

There are also air vents but no temperature controls, and while there are USB ports, there is no regular household-style plug in the cabin. 

The glass in the windows is laminated, while the roof is double glazed, which MG tells me is Australian summer-proof, but I guess we'll know for sure in a couple of months.

There’s no shortage of cargo room either. There’s a 32-litre frunk up front, and there’s 646 litres in the boot with the rear seats in place. They’re 60/40 split, and if you drop them, luggage space grows to 1621 litres.

The towing capacity is a braked 1500kg, too, but I don’t expect to see many of these towing a camper trailer around.

Premium play means more premium prices, and my IM6 Performance will set you back $80,990 on the road. That might have just sent your eyebrows skyward, but keep in mind it’s faster than some Ferraris, and is swimming with high-end tech, so the bang-for-buck factor is actually still pretty good.

There are cheaper ones, too. The single-motor Premium grade is $60,990 drive-away, albeit with less power and slower charging. Then there’s the Platinum, with a bigger battery and faster charging, which is $69,990

The Performance, though, gets everything IM has to give, including an 800-volt architecture, which means super-fast charging, as well as twin motors, brutal acceleration, a decent driving range and adaptive air suspension.

Elsewhere, you get LED lighting, a big and insulated glass roof, and 20-inch alloy wheels. Inside, there are thick and soft synthetic leather seats that are heated and cooled in both rows, a banging 20-speaker sound system, and wireless charging to pair with wireless Apple CarPlay and Android Auto.

There’s also 'active noise cancellation', and a seat-aware digital assistant which is about the best, and fastest, I’ve ever used. The IM6’s speaker system can locate where a voice is coming from, so any passenger can use the assistant. For example, if you’re in the backseat and say 'hey IM, lower my window', only your window opens. It’s a technology that I specifically remember the German brands crowing about not so long ago.

There’s also a 10.5-inch central touchscreen that controls much of the vast 26.3-inch screen that runs from in front of the driver to the centre of the cabin, as well as clever little magnets embedded in the dash in front of the driver, as well as in the back of the front seat headrests, that are designed to hold phones, iPads or other little accessories.

Also cool is the IM6’s self-parking tech, but there’s also a relatively useless crab walk function, which leans on the rear-wheel steering system to drive diagonally at slow speeds. I’m still not entirely sure when you’d use that one, to be honest.

Honestly, it’s a lot of stuff, and a lot of tech.

There are two engines on offer. The 3.0-litre (M256) in-line six-cylinder turbo-petrol GLS 450 4Matic, and the 2.9-litre (OM656) in-line six-cylinder turbo-diesel GLS 400 d 4Matic.

The all-alloy, twin-scroll single-turbo petrol engine delivers peak power of 270kW from 5500-6100rpm, and maximum torque of 500Nm across a broad plateau from 1600-4500rpm. It also features a 48-volt electrical system driving the ‘EQ Boost’ set-up, able to deliver an extra 16kW/250Nm for short periods. The integrated starter-generator also enables energy recuperation.

Although the all-alloy, twin-turbo diesel features variable valve lift it gives some ground on power, offering up 243kW between 3600-4000rpm, but torque is a solid whack, with 700Nm on tap from 1200-3000rpm. Worth noting, that to minimise emissions this engine features a “selective catalytic reduction converter” in the exhaust, which brings with it the use of an ‘AdBlue’ reducing agent. The separate AdBlue tank has a capacity of 31.6 litres.

The nine-speed auto transmission is the same in both versions, although the diesel has a slightly lower final drive ratio.

This is the real party trick of the IM6, because there’s a nuclear power plant under the metal somewhere. All up, the twin-motor setup produces a total 578kW and 802Nm, though I suspect you’re never accessing all the grunt all at once. Still, 100km/h zips by in 3.4 seconds, and the top speed is 239km/h. For the record, that’s exactly as fast the Ferrari Roma Spider I recently handed back, so yeah, it’s properly supercar quick.

Claimed fuel economy for the combined (ADR 81/02 - urban, extra-urban) cycle for the GLS 450 is 9.2L/100km, the more frugal GLS 400 d trimming that to 7.7L/100km. The petrol 450 emits 210g/km of CO2 in the process, the diesel 400d dropping that slightly to 202g/km.

Stop-start is standard, you’re looking at premium unleaded for the 450 GLS, and you’ll need 90 litres of dinosaur juice to full the tank on both models.

Also on board is a 100kWh Nickel-Cobalt-Magnesium battery that produces a WLTP driving range of 505kms. Pretty good.

Charging is strong, too. The high-tech platform allows for 396kW DC fast charging, which is faster than what is currently offered in Australia. The claim is 30-80 per cent charged in 15 minutes. There’s also an external vehicle-to-load (V2L) port.

Merc claims the GLS 450 will sprint from 0-100km/h in 6.2sec, and the 400 d in 6.3sec. Not hanging around for a 2.5 tonne mothership. But the standout is the 400 d’s torque. All 700Nm of it available from just 1200rpm to 3000rpm; right in the mid-range sweet spot.

The nine-speed auto transmission is smooth yet responsive, with paddles on the wheel for manual shifts when you want to pick the ratio. The combination of effortless grunt and the nine-speeder keeping things on the boil is an impressive one.

Suspension is by double wishbones at the front and multi-links at the rear, and while you can feel the weight in cornering, the standard Airmatic air suspension (which does away with steel springs) is superb in terms of ride comfort and body control.

We took a deep breath and pushed enthusiastically through a series of sweeping corners and the fat (285/45 fr - 325/40 rr) Continental ‘PremiumContact 6’ rubber wrapped around our car’s (optional) 22-inch rims gripped hard.

The ‘4Matic’ all-wheel drive system also seamlessly shuffles torque between the front and rear axles (theoretically up to 100 per cent in each direction).

Merc has put extra focus on body rigidity, the tuning of engine and suspension mounts, and sound absorption, and it shows. The GLS 400 d is beautifully refined on the highway. A neat touch is the car automatically lowering 15mm at motorway speeds or when ‘Sport’ mode is selected.

Steering is electromechanically assisted, and Merc says the front suspension geometry has been revised to minimise vibration through the wheel. And yes, feedback is minimal, but unfortunately so is road feel with only a general connection between your hands on the wheel and the front tyres on the bitumen.

When you’re steering a large beast like this, often with something substantial hitched to the back, you want to know braking performance is up to the task, and the GLS’s big ventilated discs all around deliver reassuringly strong stopping power, with nice, progressive pedal feel to boot.

The seats are adjustable six ways to Sunday, but beyond that they’re comfortable and supportive, even over long stints behind the wheel.

We stayed on the bitumen, because, let’s face it, that’s where this car will spend 99.9 per cent of its time, with the exceptions of the boat ramp, a ski weekend or pony club.

For those special occasions the optional ‘Off-road engineering package’ adds a low-range transfer case, inter-axle locking, hill descent control, and under body armour for more serious work.

First things first, don't get too distracted by the word "performance" here. The IM6 doesn't act like a performance car, it feels bit too plush, and bit too digital, for that.

But that's not necessarily a bad thing. Performance cars are often loud, raucous and uncomfortable, and the IM6 is none of those things. Instead, those mountains of power and torque make silky, silent progress absolutely effortless, which feels pretty premium to me.

MG makes a big deal of how much work went into insulating the cabin from noise – with active noise cancellation joined by double-paned insulated glass – and it is a properly calming and quiet space.

Also strong is the suspension, with the adaptive air setup soaking up most bumps and bruises, but I found it can clang over really solid bumps, sounding like it's bouncing off a stopper. The steering is solid, too, with a nice weight, if not overly talkative in the feedback department, while the rear-wheel steering helps eat into the turning circle for tight three-point turns.

The downside, though, is that it all feels a little too digital, and like there's been a little too much overthinking gone into it. Having to push a button to see behind you in a hurry is bonkers (see my explanation in the Safety section below), and the secondary screen is more annoying than intuitive. And there were several bings or bongs I couldn't even identify. All of which interrupts the otherwise calming nature of the drive experience.

There is a long list of safety aids on the IM6, and I won't detail the lot here. But I will call out a couple of curious mentions.

As always, the driver distraction warning is annoying, but can be switched off. And MG also counts the IM platform, or what it calls a digital chassis, as part of the safety offering. It has its own digital brain that adapts the air suspension, the rear-wheel steering and the active safety kit on the fly.

The other curiosity is the weird way you see out the back. Rather than fit a digital rear-view mirror to counteract the almost non-existent rear vision, you instead push up on a little toggle on the steering wheel to bring up a live view of what's happening behind you on the central screen.

The Mercedes-Benz range is covered by a three year/unlimited km warranty, which, like Audi and BMW continues to lag behind the mainstream market where the majority of players are now at five years/unlimited km, with some at seven years.

On the upside, Mercedes-Benz ‘Road Care’ roadside assistance is included in the deal for three years.

Service is scheduled for 12 months/25,000km (whichever comes first) with pricing available on an 'Up-front' or 'Pay-as-you-go' basis.

As a guide, service pricing for the outgoing GLS is set at $2600 per service (up-front) and $3250 (PAYG), a saving of $650 a pop. Fourth and fifth services are also available for pre-purchase ($3550 and $4900).

The IM6 is covered by a five-year, unlimited-kilometre warranty, rather than MG’S 10-year term. Capped-price servicing is offered for the first five years, with your total bill just under $3000. The service intervals are 20,000kms or 12 months.