BMW 840I vs Mercedes-Benz AMG GT

What's the difference?

If you’re the sort of buyer who wants a car that signifies a lifestyle that is ‘large and in charge’, the BMW M850i Gran Coupe could be just the thing for you. It isn’t as showy as some of its competitors, and mightn’t reach the same levels of excitement as those cars either - but it is a convincing offering in its own right, and a beautiful piece of design at that. 

The GT63 4Matic+ is a breathtaking example of everything that Mercedes-Benz and AMG are.

Ferociously fast, incredibly agile and superbly sophisticated, it should be on anybody’s shortlist, if that also includes a Porsche, Aston Martin, Maserati or even a Lamborghini. And it’s definitely much more than yesterday’s SLC ever was – for similar money in today’s terms, as it turns out.

But, around Tasmania’s glorious roads at least, the Mercedes-AMG lacks the ride comfort and road noise isolation to be a fully-rounded-out GT, and that’s a disappointment for a brand with such formidable history in making such cars.

This could be BMW’s most convincing design in years. I mean, the X5 is predictably handsome, the X3 was unexpectedly muscled, and the less said about the frumpy 1 Series and busy 3 Series (apart from the wagon… drool) the better.

To my untrained but enthusiastic eye, the 8 Series Coupe is a bit too rounded over its rear haunches, and the rear screen is just a little steep - to me, that lets its dimensions down a little. But this. This is gorgeous. 

I mean, you might have questions over the tail-light design, which is a theme across a few BMW models now. But there isn’t as much confrontation between horizontal and vertical graphics for this model as you’ll find one other big Bimmers, like the X7. 

The M850i model has BMW Laserlight headlights, which throw a sharp beam and look menacing in their signature, while the grille and bumper are strong. The stance of the car is prominent - there’s a long body, a long wheelbase, and a long body in general. The standard wheel package consists of 20-inch rims, and they don’t look disarmingly large.

As our images show, there’s a lot to talk about when it comes interior design and finishes, but the cabin doesn’t quite benefit quite as mochas you might think it would from all that real estate. I mean, with dimensions of 5074mm long (on a 3023mm wheelbase), 1932mm wide and 1402mm tall, this is a squat, yet substantial vehicle. It’s just more cramped than you’d think inside.

This is still clearly a Mercedes AMG GT coupe, like the 2014 C190 original, but a ground-up redesign sees it subtly yet significantly altered.

Some 270kg heavier than before, the larger-in-every-dimension body combines aluminium, steel, magnesium and fibre composite materials for improved rigidity and a lower centre of gravity. Length (4729mm) and wheelbase (2700mm) have been stretched by 177mm and 70mm respectively. Width (1984mm) and height (1352mm) are also up.

The nose treatment is similar to before, especially with the bulgy bonnet and signature vertical slatted grille fitted. These, combined with the LED digital headlight shape effect, is reminiscent of, but far-better executed than, the goofy-looking MG5’s face.

Underneath, it's an all-new platform shared with the SL, with the rear transaxle of the old car replaced by a permanent AWD system, leading from 46:54 front/rear weight distribution to 50:50 as a result.

That aggressive, exaggerated cab-backward/ultra-long bonnet silhouette that visually connected it with the SLS gives way to more-conventional and practical coupe proportions that is striking if not especially original, since they do look quite 911-esque. Along with the longer wheelbase and wider tracks, the result allows for two small rear seats to be fitted, while liftback cargo access remains.

Similarly, in the name of way-more usable interior packaging, Mercedes-AMG says it pushed the driving position nearly 180mm forward compared to the previous GT. Let’s see what that all looks like inside.

I recall a Mitsubishi designer telling me, once upon a time, that he dreamed of making ‘a big car on the outside with a very small interior’. Maybe he made the jump to BMW, because that’s pretty much the 8 Series Gran Coupe.

There aren’t many other vehicles on the market, of this size, that offer less space inside. The boot capacity, for instance, is just 440 litres. Competitors like the Audi A7 (535L) and Mercedes CLS (520L) easily outdo it - but at least this car has more boot than the Panamera (405L), though the BMW is a smidge bigger. The cargo space is large enough for a couple of overnight suitcases, but you’re hardly going to fit a family of four’s luggage for a week away. 

And while we’re in the “not quite what you’d expect” column, the back seat space is hardly commodious. There’s enough space for me, at 182cm, to sit behind my own driving position, but not without wishing for a bit more toeroom, headroom and knee space. 

The big centre console section eats into the space in the rear, justifying the brand’s “4+1” seating claim, and unpleasantly it has a hard plastic finish to rest your leg against. Getting in and out of the second row isn’t easy for bigger people, and it’s quite a squat down into the rear seat - it really has taken inspiration from its squashy-back-seated predecessor in that regard.

If you have smaller rear-seat occupants, however, there will be catered for with dual ISOFIX and three top-tether points, plus there are air vents with climate controls (quad zone in total), and two USB-C ports as well. There are sun-blinds on the rear windows, too, which is a plus, and there is a pair of cup holders in the fold-down armrest, and map pockets in the seat backs, too. The door pockets are near-useless, though.

The front seats score better practicality, with bottle holders in the doors, bigger and sturdier cup holders, a covered centre storage bin between the seats with a USB-C port, and a wireless phone charger (Qi) with standard USB port in front of the gear selector.

Above that is the weird, very out-of-place quick buttons (1-8) that BMW could easily do away with, and further up are the controls for the climate control (thankfully with hard buttons for fan speed and temperature), and above that is the media screen, a familiar looking 10.25-inch touch display running BMW OS 7.0. 

The screen is quick and crisp, and is backed up by the rotary controller and buttons on in the centre console area. There’s wireless Apple CarPlay (now at no cost for three years), as well as a built-in SIM card for 4G data and access to the BMW Online news and weather stations, accessed through the screen.  

It’s all pretty easy to use, and the sound system is excellent - the standard setup consists of 16 speakers, with DAB+ digital radio, Bluetooth and USB plus the smartphone mirroring tech, provided you don’t have an Android device, as Android Auto is still missing from BMW’s range.

It’s a nice cabin, but I couldn’t help but thinking that I’d want a little more differentiation from the lesser models in the range if I was spending this much. Especially considering the optional cost of the interior trim fitted to our test car - see below for more detail.

The first impression inside is that of space, despite the falling roofline and coupe-like upsweep of the side windows and you look back. While, again, similar to a 911s, a kink at the door gives the GT a unique character.

Even larger people will appreciate the generous amounts of room up front, with space to stretch, sat in sumptuously comfy bucket seats. Note that the standard ones are better than the racier but firmer Sports versions.

The driving position is perfect, ahead of a dashboard that is very typical modern Mercedes in appearance and layout.

To that end, the tablet-style integrated touchscreen (11.9 inches) is clear, fast and intuitive once time is taken to learn it. And points are also won for the multi-configurable electronic instrumentation, that allows for a variety of screens, including track, classic and minimalist views.

The trademark turbine air vents, the quite beautiful material and trim finishes and just the general solid feel are further typical contemporary Mercedes cabin treatments, as are the excellent ventilation and ample storage options.

And while rear vision isn't great, that's what cameras are for. It's all pretty much on brand.

It is a shame, given how elevated the Mercedes-AMG engineering is underneath, that the GT’s interior look and ambience is so similar to those of a (albeit higher-spec) C-Class or GLE. It's simply not as special as some of the company’s previous sports cars.

More annoyingly, the ride is too firm and bumpy for a GT, and this has the unhappy effect of provoking random rattly trim sounds within the cabin. It’s a bit like scrunched-up cellophane. In a $420K (as tested) Merc, that’s very disappointing, especially as it can be heard over the copious amount of road and tyre noise droning through, particularly on coarser bitumen surfaces.

Further back, the rear seat is strictly two-plus-two, and nobody over 150cm tall is recommended to travel there by Mercedes itself. That sloping roofline is the culprit. That said, brief trips with a bowed head are possible, as the fixed cushions and split-folding backrests are actually surprisingly comfy. But only for short journeys. Kids should love it though, and the second row does open up the GT’s usefulness enormously.

As does a near-doubling of the AMG’s cargo capacity, jumping 146 litres to 321L with backrests erect, to a whopping 675L (+325L) in two-seater mode. The flat floor is accessed via a large electrically-operated liftback door, offering quite a large aperture for easy loading/unloading.

Having no spare wheel helps here, with a tyre inflation kit included in lieu of that.

Meanwhile, at the front, under the bonnet, things have definitely changed for the better as well.

Starting from $370,400 (all prices are before on-road costs), the Mercedes-AMG GT63 4Matic+ is priced and positioned as something of an eagle amongst some pretty delectable doves, given its combination of four seats, 430kW of power, 800Nm of torque and four-wheel drive.

No rival equivalents can match the Mercedes on paper. The 398kW/610Nm 911 Carrera 4 GTS T-Hybrid offers less power but starts from $400,000-plus. The 410kW/650Nm GranTurismo Trofeo begins at $450K, the 500kW/800Nm DB12 from $455K and the 404kW/470Nm Continental GT from $460K.

Only the 460kW/750Nm BMW M8 Competition comes closest to the Mercedes-AMG, from $380K.

Side note, today’s GT is only slightly more expensive than what the 450SLC was nearly half a century ago when adjusted for inflation.

And, just like with that classic old Benz, it shares much with the brand’s legendary SL convertible stablemate – including, in this case, standard all-wheel drive and active rear-axle steering… aka 4WS to select third and fourth-generation Honda Prelude owners out there.

What else does $400K-plus buy you? As you’d expect, the GT63 4Matic+ comes choc-full of standard equipment, much of it typical of the luxury coupe breed, with leather-covered and electrically operated everything.

How about a front-axle lift system with GPS-enabled memory that automatically raises the GT’s nose to help clear bumps and then remembers to do so next time?

There are climate-controlled AMG sports seats with inflatable bolstering and massaging functionality, a fixed glass roof, a head-up display, augmented-reality satellite navigation, 360-degree surround views, performance telemetry data as part of an extensive multimedia system, an 11.9-inch portrait touchscreen, 11-speaker Burmester audio, a handsfree-powered tailgate, 21-inch alloys and cutting-edge driver-assist safety tech. More on that in the Safety section below.

Then there are the myriad option packs, bumping the GT63’s price up towards $500,000. These include a $2.7K seat trim package; a $10K AMG Night Package that adds darker trim treatments (often where chrome was); an aerodynamics package with fixed spoiler replacing the standard active spoiler; a $2.6K AMG Performance Seat package; a $13K Carbon Fibre package and $13.2K Ceramic Brakes.

Now, while the new GT does ditch the previous model’s unique rear transaxle spaceframe pioneered by the gull-winged SLS of the early 2010s, the resulting longer wheelbase and shorter overhangs do provide less outlandish and more practical design.

Let’s check that out in more detail. 

If you’re going for the M850i, you’re getting the big bopper engine. It’s a 4.4-litre twin-turbo V8 petrol engine, and it isn’t short on horsepower.

The outputs for this engine are 390kW of power (at 6000rpm) and 750Nm of torque (from 1800-4600rpm). Hardly numbers to sneeze at.

And the performance figures are exceptional, too: the claimed 0-100 km/h time is just 3.9 seconds. That’s because there’s the traction of BMW’s xDrive all-wheel drive system, and shifting gears is an eight-speed automatic transmission.  

For what it’s worth, your humble reviewer saw a 0-100km/h time very close to that (4.2sec). 

The quoted kerb weight for this model is 1995kg.

There’s a plaque signifying which engineer “handcrafted” the GT’s engine – in this case, the famous M177 in 3982cc, 4.0-litre twin-turbo intercooled V8 petrol guise.

Delivering 430kW of power at 6500rpm and 800Nm of torque from 2500-4500rpm, it sends drive to all four wheels via a nine-speed multi-clutch transmission (dubbed MCT in AMG-speak), catapulting the GT63 4Matic+ from 0-100km/h in just 3.2 seconds, on the way to a top speed of 315km/h.

How does it do that?

With AWD, the GT is now nearly 15 per cent heavier than before, but it still manages a punchy 218kW/tonne. Active aerodynamics over, inside and under a more-rigid body structure also helps.

The AMG 4Matic+ AWD system goes from 50/50 front/rear, to 100 per cent rear, variable torque distribution according to conditions and settings, and backed up by an electronic limited-slip differential. Among the many driving settings are Race Start, Drift Mode and good-old Comfort, if it all becomes too much.

Also keeping all that performance in check is a high-performance composite brake setup with improved cooling for faster responses.

Interlinked active roll bars improve body control, the five-link independent suspension features adaptive dampers for a softer ride.

And, as for that 4WS tech, the rear wheels steer opposite to the fronts at up to 100km/h (by some 2.5 degrees) for tighter and tidier handling, or 0.7 degrees in the same direction above 100, for greater stability and road-holding.

Its effect on the way this near-two-tonne coupe zigs and zags around corners is something you need to experience to really appreciate.

You can’t really expect a big V8 beast like this to be a fuel miser, and it isn’t.

The claimed consumption is 10.7 litres per 100 kilometres. Which is alright, honestly, given the sheer volume of car you’re driving. 

But on my test - which consisted of more than 300km of mixed driving, including days of city commuting, some twisty mountain driving, and all the freeway floundering to get there - I saw an at the pump real-world figure of 15.4L/100km.

That’s not very efficient, and it’ll be expensive to run on the daily — yet the argument could be made that if you’re spending this much on a car, fuel costs won’t matter much to you. But with a small fuel tank capacity of 68 litres, it could become a little inconvenient as you’ll be seeing a lot of your local servo.

Actually, the GT’s economy isn’t horrendous considering how fast it can go.

Even blasting a few times around beckoning country roads, we managed an indicated 13.0L/100km, which is an improvement on what Mercedes-AMG says the GT averages the 14.6L/100km average that Mercedes-AMG officially states.

That translates to a carbon dioxide emissions rating of 334g/km.

Using 98 RON premium unleaded petrol, an average of just under 480km between refills of the 70L tank is possible. The urban run sees consumption rocket to 21.8L/100km (for just 321km of range), or 10.4 out on the highway run, meaning that over 670km is possible should you decide to drive in a docile manner.

It’s an impressive thing, this M850i xDrive Gran Coupe. But I’m just not sure who it’s trying to please.

It’s not the sort of German monster coupe-sedan that grabs you by the scruff of the neck and throws you around with its mammoth acceleration. Not unless you poke it and prod it and make it really angry.

And that might be exactly what you want to do - put it in Sport mode, sling the shifter across to sport or manual mode, hear the exhaust open up from a pursed-lip tongue-click to an open-mouth growl. 

You’ll push hard on the accelerator, watch the tacho needle jolt to the redline, and if you’re in auto mode you’ll feel the transmission whipcrack as it shifts rapidly up through the gears as you’re shoved back into your seat. Before you know it you’ll be in licence-loss zone, and you won’t have even made the tyres chirp - that’s how immense the traction from the all-wheel drive system is.

You’ll brake hard into a sharp bend, and you’ll feel the front end dip and the body of the car change direction more readily than you’d think given its size as you turn in. The steering response will meet your expectation, with rapid reaction to adjustments mid corner. And the Active Roll stabilisation system will mean you’re not being thrown around in your seat, because it’s sitting flatter and truer than you might have expected - you’ll notice how it works extremely well in conjunction with the car’s torque-vectoring-by-braking system. There’ll be little weight shift or body roll to be counteracted, and that’ll inspire you to push it even harder.

Put it in manual transmission mode and you’ll rejoice that it won’t overrule you and shift up, but you’ll also feel shortchanged because it gets to the end of its limit very quickly. And when it hits redline, it emits a breathless little cough rather than a “oh maybe I should stop” rev-bounce noise.

But, if you’re like me, you might be doing all this with a niggling thought in the back of your mind that, while this car is technically really good and it’s a clinical performance car, you might just think to yourself, “I’m not having as much fun as I thought I would”.

A Mercedes-AMG would be more fun; it’d be more raucous, more of a muscle car experience. An Audi RS7 (at least the previous one) would be noisier, brasher, more theatrical than this car. And likewise, a Porsche Panamera - no matter the model you go for - would be more entertaining in the bends.  

Maybe it’s just a bit too predictable - and maybe that’s a result of this car being honed for drivers who will spend more time on the Autobahn than anywhere else. I have to say, there are much, much worse (and slower) ways of getting from A to B, and the highway cruising comfort of the M850i Gran Coupe was what impressed me most. 

It’s also surprisingly adept at urban driving duties, coping well with unpleasant city surfaces, though potholes can still upset things because of the stiff-sidewalled run-flat tyres. The suspension does an exceptional job otherwise, however, and I switched between the Adaptive drive mode and Comfort mode for my commuting duties. Both proved comfortable and controlled.

The M850i is by no means a failure when it comes to fulfilling the expectations you might have of a luxury sports sedan of this size. In fact, it’s close to a distinction. But I just can’t help thinking that it’s not as much an ‘M car’ as that M850i badge might have you believe it should be.

Nobody will drive the GT63 4Matic+ and think, ‘Oh, this is OK’, because its breadth of performance is phenomenal.

No matter which mode you're in, from Comfort through to track-tuned Race, the Mercedes-AMG blends forceful pace and commanding control without ever breaking a sweat.

Flex your right foot and the two-tonne coupe bounds into action like a giant on a mission, striding past posted speed limit signs in nanoseconds and way, way faster than the law will stand if diligence isn’t exercised.

And there’s no point relying on seat-of-your-pants sensations, either, because the chassis below embraces the road with an almost zealous devotion. Which is astounding, given how agile the four-wheel steering-enhanced handling is.

The 63’s super power is exactly that – it dulls your sense of speed. One tester admitted to exceeding 150km/h before noticing. An odd confession considering the sonic boombox that is the bi-turbo V8’s howl.

But jailbait performance is not even the 63’s most lingering joy. That would be its steering perfection, that delivers that rare trifecta of keenness, crispness and communication. The wheel feels eager and alive in your hands, even when powering between tight turns, backed up by sensational grip and control. How can a two-tonne GT handle so sharply?

Warm, dry roads were the order of the day, so we can’t tell you how the 4Matic+ permanent AWD system deals with wet or slippery surfaces, but the slick multi-clutch transmission, seamless torque-vectoring tech and sticky tyres more than cope with the 63’s formidable outputs.

So, that's the gushing part out the way, then.

Despite the adaptive dampers, rigid architecture and exquisitely sophisticated suspension, the ride is simply too stiff in Comfort mode, and downright jittery on some of the Tasmanian roads we tested on, for the 63 to be considered a true luxury grand tourer. It just isn't comfortable, luxurious or supple enough.

Plus, grippy as they are, the 21-inch wheels transmit too much road and tyre noise through to the cabin, meaning that the GT isn't as quiet as you'd hope. Add the aforementioned trim squeaks, and the expected cocooned silence isn’t always there.

The upshot is that the 63 possesses more of a sports car character than a luxury GT character. Great news if you're a 911 type buyer and are seeking a high-performance 2+2 alternative, but a disappointment if comfort and refinement are priorities.

Still, it is impossible not to be deeply moved by this Mercedes-AMG.

While the GT doesn’t score an ANCAP rating – probably because it’s too expensive to crash test – we’d wager that it would be above-average, given Benz’s track record as a pioneer in this field.

That’d due to the scores of active, passive and driver-assist safety features fitted, from multi-faceted autonomous emergency braking (AEB) and lane-support systems to Mercedes’ PRE-SAFE tech that anticipates a crash and then prepares the car for impact.

More specifically, the GT includes Active Lane Change/Keep Assist, adaptive high beam as part of its megapixel LED set-up, adaptive cruise control, Cross-Traffic Assist, Evasive manoeuvre support, an emergency services call-out system, 360-degree camera views, pedestrian protection bonnet and eight airbags.

In other Mercedes products of today, AEB operating parameters are 7-80km/h for vulnerable road users like pedestrians and cyclists, and from 7-250km/h for vehicle-to-vehicle, while the lane-keep support systems operate between 60-200km/h.

Finally, there are ISOFIX child-seat anchorages in the front passenger seat and two in the rear seats.

BMW backs its cars in Australia with a three-year/unlimited kilometre warranty.

You may be confused if you head to the BMW site and see that M models and 8 Series models aren’t covered by BMW’s pre-pay capped price servicing plan (as I saw when testing this car), but CarsGuide can confirm that the 8 Series is indeed covered - unless it’s the real M8, not this M850i jigger. 

BMW Australia has clarified that the Service Inclusive pack for five years/80,000km of maintenance cover is $2490 for Basic cover (no brakes/pads, no wiper replacement), or $5641 for the more comprehensive Plus pack. Hardly affordable, but nor’s the car. 

The company uses a condition-based servicing program, too - there are no set service intervals, but the car will tell you when it needs maintenance based on how you drive it.

For what it’s worth, we ran the numbers on resale value using Glass’s Guide predictive analysis tool, and after three years/40,000km the expected retained value for this version is approximately 66 per cent - which is impressive.

What’s the GT like to own?

Mercedes-Benz offers a five-year/unlimited km warranty, with five years of roadside assistance. This is average for most mainstream and luxury brands, but superior to most sports-car makers like Porsche and Lamborghini.

Intervals are every 12 months or 20,000km, and while no capped-priced servicing is offered on the GT, pre-paid three-, four- or five-year service plans are available, ranging from $5165, $7700 and $8665 respectively.

Big performance demands big maintenance bills, it seems.