BMW M8 vs Porsche Cayenne

What's the difference?

With dramatic looks, a luxurious spec, and impeccable quality, the BMW M8 Competition Gran Coupe remains supremely well controlled as it delivers eye-widening performance and amazing dynamics. But there’s an ‘edge’ to the experience you need to be ready for. If I was determined to head for the Aussie ‘fast lane’ in a BMW 8 Series Gran Coupe I’d opt for the M850i and pocket a lazy $71K (enough for a cheeky M235i Gran Coupe to add to your collection).

Of all the super SUVs I've piloted, the Porsche Cayenne Turbo GT is the best all-rounder in terms of performance, comfort, cabin technology and style.

As a family car it's roomy, practical and easy to use and drive daily.

As a performance car the Turbo GT is stupidly quick, with the agility of a sports car. Sure, a 911 would leave it behind on a twisty race track, but this SUV is close to having that sportscar experience and keeping your family, as well.

Want to start a vigorous car enthusiast discussion (more a verbal punch-up)? Simply ask whether a four-door car can be a coupe.

Traditionally, the answer is no, but over time numerous automotive brands have applied that description to cars with more than two doors, including SUVs!

So, here we are. A four-door ‘Gran Coupe’, and the M8 Competition version retains the smoothly tapering turret and frameless side glass that help give selected BMW four-door models the same swoopy, coupe look.

At close to 4.9m long, a fraction over 1.9m wide, and under 1.4m high, the BMW 8 Series Gran Coupe has a firmly planted, low-slung, wide-track stance. Always a subjective call, but I for one, think it looks stunning, especially in our test car’s ‘Frozen Brilliant White’ matt paint finish.

In an era of comically oversized BMW grilles, things are relatively under control here, with a bright black finish applied to that ‘kidney grille’, as well as the huge front bumper air intakes, front splitter, front fender vents, exterior mirrors, window surrounds, 20-inch rims, lip spoiler on the boot, rear valance panel (incorporating a functional diffuser), and quad exhaust tips. The roof’s black, too, but that’s because it’s made of carbon-fibre.

Overall the M8 Competition Gran Coupe is a compelling combination of strong, confident character lines along the bonnet and lower flanks, with tightly wrapped curves following the high hip line, and more organically irregular, yet distinctly BMW shapes in the head- and tail-lights. 

The interior is a beautifully balanced design with a broad centre console sweeping up to the middle of the dash and wrapping around to focus on the driver, in typical BMW fashion.

 The multi-adjustable sports front seats are immaculate, with high-end quilting in the centre section matching a similar treatment in the doors. The dark grey (full) leather trim is offset by carbon and brushed metal trim elements for a cool, calm and focused feel.

Crack the bonnet open and a spectacular ‘BMW M Power’ carbon cover dressing the top of the engine is guaranteed to impress friends and family.

This might be a personal thing but to me nearly all Porsches look better from the back than the front.

It's the wide stance and powerful haunches, the hunkered down suction-capped-to-the-road look that does it for me and the Cayenne Turbo GT, despite being an SUV, passes this important Porsche checklist item.

The GT aero kit only serves to make this SUV look more of a beast, and the gold-bronze looking satin Neodyne wheels are a Porsche theme that I've not always been a fan of, but I get the historic connection.

If only the Turbo GT could look a little less like other Cayennes from the front. This is the king of the SUV range and despite the apron and bumper already being exclusive to this model, there should be more.

Vents in the wheel arches, carbon bonnet with nostrils GT3-style perhaps? Or is that going too far? If you do want something more lairy then there's always the Urus.

The Cayenne Turbo GT's cabin is stunning in its plushness and modern surprises such as the passenger display, the hoodless instrument digital cluster, the lashings of Race-Tex upholstery everywhere. It's perfectly Porsche. High-performance meets high-end.

It's also highly practical. Let's talk about that.

Of the M8 Competition Gran Coupe’s 4867mm overall length, 2827 of it sits between the front and rear axles, which is a pretty healthy wheelbase for a car this size (and 200mm more than the 8 Series two-door coupe).

Space up front is generous, and one upside of a four-door, rather than two-door coupe, is you’re not struggling quite so much for space to get in and out when parked next to other cars.

Once inside, there’s plenty of storage up front, with a large lidded box/armrest between the front seats, twin cupholders in the centre console, as well as another covered area for wireless phone charging and extra bits and pieces in front of that. Long door pockets provide space for bottles, and the glove box is a decent size. There’s 12V power as well as USB sockets for media connection, with charging outlets in support.

At first glance you’d swear the rear seat was designed as a two-seater only, but when push (literally) comes to shove a centre passenger can squeeze in, legs straddling the rear console.

In terms of legroom, at 183cm (6’0”) I could sit behind the driver’s seat set for my position with knee room to spare, but headroom is another matter, with my noggin making solid contact with the soft Alcantara headlining. It’s the price you pay for this car’s racy profile.

There’s a neatly trimmed storage box and two cupholders in the fold-down centre armrest, plus door pockets with enough room for small bottles. The rear console houses dual climate controls, twin USB power sockets, and a small oddments tray, as well as buttons for the optional rear seat heating fitted to our test car ($900).

The 440-litre boot is a bit like the car itself - long and wide, but not very high. The rear seat split-folds 40/20/40 if you need more space, and the boot lid is automatic with a hands free function. But don’t bother looking for a spare of any description, a tyre repair kit is your only option.

The Porsche Cayenne Turbo GT only makes one compromise on practicality and that's the removal of the middle seat in the back, which, with just two kids isn't used all the time but on average we might need it once a week for school mates and cousins.

Instead of a middle seat there is a shallow tray, which will fit a phone or in our case leaves and rocks found at the park.

So, yes, the Turbo GT is a four-seater only, but this is a spacious, large SUV with good head and legroom, wide-opening doors for easy entry and exit, and air suspension which can raise and lower the height for easy access.

Storage is excellent with enormous door pockets in the front and back and there are four cupholders.

There's a wireless phone charger in the front and two USB-C ports as well, plus two USB-C sockets in the back.

Four-zone climate control means the kids in the back can set their own temperatures. They also have heated seats.

I was disappointed to see there aren't sunshades for the rear windows - pretty vital in Australia where it feels like we're only about 50 metres away from the sun.

The Turbo GT's 576-litre boot just managed to fit our pram and a week's shopping, which is our minimum standard for living. Any more space is a bonus.

The Turbo GT is the king of Cayennes, so it shouldn't surprise anybody that it's also the most expensive with its list price of $364,700.

Lamborghini's Urus lists for $409,744  and is the Cayenne Turbo GT's not-so-subtle Italian cousin, sharing the same platform and engine.

Both are in my mind the best performance SUVs on the planet. It just depends how conspicuous you want to be.

Then there's Bentley's V8 Bentayga which isn't blessed with the Porsche's good looks but would still be all over the Cayenne if the two happened to meet at a race track.

So, why is the GT Turbo the king of the Cayennes? What makes it better? For all the reasons you'd think - it's the fastest, most powerful, most luxurious and most equipped Cayenne in the range.

We'll get into mind-bending engine and performance specs soon, but first let me take you through the standard features on a car that's anything but standard.

Coming standard and exclusively to the Turbo GT are 22-inch 'GT Design' wheels in satin 'Neodyne' with full-colour Porsche centre caps, an active rear spoiler, Turbo GT front apron, dual titanium exhaust, rear apron with diffuser, 'SportDesign' side skirts, wheel arch extensions, a lightweight carbon roof and tinted LED HD-matrix headlights.

Inside, and also exclusive to this grade, is the 'GT Interior Package' with 'Race-Tex' upholstery throughout with 'Deep Sea Blue' stitching on the front seats and centre console and the armrests and dashboard.

There's also the 'Carbon Interior Package' which includes dashboard and door trim elements.

Race-Tex trim is applied to the 'GT Sports' steering wheel, roof lining and gearshift, too.

The adaptive active air suspension, which can lower the car by 15mm, is standard and only available on the Turbo GT, too.

The soft-close doors are standard (a cost option on lower grades), as are the stainless steel pedal covers.

The rest of the features are also found on lower grades and include the 12.65-inch digital instrument cluster, head-up display, proximity unlocking, 12.3-inch multimedia touchscreen with sat nav, wireless Apple CarPlay and Android Auto, digital radio, a 10-speaker Bose sound system, heated front seats, rear privacy glass and an auto tailgate.

Four-zone climate control is standard on the GT Turbo, too, and so are heated rear seats.

Our car had several options fitted such as the front passenger display ($2860) and the Deep Sea Blue Accent Package.

The passenger display is a crowd pleaser, but as a family car my kids felt like they were missing screens in the back seats, too. Well, in my day...

The M8 Competition is powered by an all-alloy, 4.4-litre twin-turbo V8 engine, featuring direct-injection, as well as the latest version of BMW’s ‘Valvetronic’ variable valve timing and ‘Double-VANOS’ variable camshaft control, to produce 460kW (625hp) at 6000rpm, and 750Nm from 1800-5800rpm.

Designated ‘S63’, the engine’s two twin-scroll turbos are located, along with a cross-bank exhaust manifold, in the engine’s (90-degree) ‘hot vee.’ 

The idea is consistent transmission of exhaust energy to the turbos for improved response, with the reversal of usual practice completed by inlet manifolds positioned on the engine’s outer edges.

Drive goes to all four wheels via an eight-speed ‘M Steptronic’ (torque converter) auto transmission with ‘Drivelogic’, and dedicated oil cooling, as well as BMW’s ‘xDrive’ all-wheel drive system.

The xDrive set-up is built around a central transfer case housing an electronically-controlled, variable multi-plate clutch, with front to rear drive distribution set to a default 40:60 split.

The system monitors multiple inputs including, wheel speed (and slip), acceleration and steering angle, and is able to vary the ratio up to 100 per cent rear thanks to the ‘Active M Differential.’ 

As a middle-aged parent with two children, a Porsche that I don't have to crawl into and out of like a cubby house is a great thing.

What's even better is that this ‘easy access' Porsche is every bit as brutally powerful and fast as the quintessentially ‘pure' Porsche, the 911. Actually, it's more powerful and faster.

The Turbo GT's twin-turbo 4.0-litre V8 petrol engine makes 485kW and 850Nm with drive going through an eight-speed transmission to all four wheels.

In comparison, a Porsche 911 GT3 RS, arguably the most brutal and anti-social 911, has 386kW/485Nm.

I haven't made a mistake. Those are the real numbers. And it's only when you step on the accelerator in the Cayenne Turbo GT, and it feels like somebody's sat down on your chest, that you realise what a big deal this is.

That is such a colossal amount of oomph that this 2.2-tonne family SUV can accelerate from 0-100km/h in 3.3 seconds.

The 911 GT3 RS can do it in 3.2 and it has a roll cage and a fixed rear wing the size of a bedroom door.

And yes, we're now coming into a digital age where Teslas and other electric SUVs are quick, too, but can they go around corners like a Porsche Cayenne Turbo GT?

Do they have the same rumble and roar as a twin-turbo V8 that's terrifying and enticing at the same time.

The correct answer is, absolutely not.

Claimed fuel economy for the combined (ADR 81/02 - urban, extra-urban) cycle is 10.4L/100km, the M8 Competition emitting 239g/km of CO2 in the process.

Despite the standard auto stop/start function, over a week-long combination of city, suburban, and freeway running we recorded a (dash-indicated) average of 15.6L/100km.

Pretty thirsty, but not outrageous when you consider this car’s performance potential, and the fact that (purely for research purposes) we exploited it regularly.

Recommended fuel is 98 RON premium unleaded, and you’ll need 68 litres of it to fill the tank. That equates to a range of 654km in line with the factory claim, and 436km using our real-world number as a guide.

Seriously? This is a 2.0-tonne twin-turbo petrol V8 with a 90-litre fuel tank. Even the Porsche specs sheet doesn't understand the question because in the column for fuel efficiency there are three letters - tbc.

My own testing saw me record 22.5 L/100km at the fuel pump, which means I enjoyed driving the car very much.

A little digging around reveals Porsche globally claims the Turbo GT will use 12.6L/100km, over a combination of open and urban roads.

You might not have as much fun as I did but easing back a little might get you closer to the 700km of range this more frugal consumption figure appears to offer.

While efficient it isn't, I'm not going to mark the Turbo GT too much here because compared to its petrol rivals the fuel consumption is what I'd expect from such a high-output heavy SUV.

There’s something teutonically symmetrical about the way the M8 Competition Gran Coupe delivers its prodigious thrust.

Peak torque of no less than 750Nm is available from just 1800rpm, remaining on full song across a broad plateau all the way to 5800rpm. Just 200revs later (6000rpm) peak power of 460kW (625hp!) takes over to finish the job, with the rev ceiling sitting just over 7000rpm.

That’s enough to slingshot this 1885kg bruiser from 0-100km/h in 3.2 seconds, which is supercar fast. And the engine and exhaust noise produced by the 4.4-litre twin-turbo V8 during such rapid acceleration is suitably brutal, courtesy of electronically-controlled flaps in the system opening up. 

On a more civilised drive you can reduce the exhaust noise via an ‘M Sound Control’ button on the centre console.

The eight-speed auto is fast and positive, especially in manual mode, which dials up the fun via wheel-mounted paddles. And when it’s time to direct this car’s forward momentum into lateral movement BMW has brought in the engineering heavy artillery.

Despite its frameless door body structure the M8 Competition Gran Coupe feels solid as a rock thanks in no small part to its ‘Carbon Core’ construction, using four primary components - carbon-fibre-reinforced plastic (CFRP), aluminum, high-strength steel, and magnesium.

Then the ‘Adaptive M Suspension Professional’ (with active anti-roll stabilisation), the tricky xDrive continuously variable AWD system, and active M Sport diff combine to keep everything under control.

Suspension is a double wishbone front, five-link rear arrangement, with all key components in alloy to minimise unsprung weight. In concert with the electronic wizardry on-board, it helps keep the M8 buttoned down with only modest body roll in enthusiastic cornering, as the rear-biased AWD system seamlessly distributes drive to the axle and wheels that can make best use of it.

The price you’ll pay for the track-ready tune is in compromised ride comfort. Even in the ‘Comfort’ setting, the M8 Competition is firm, and feels corrugations and imperfections to a surprising degree.

An alignment of the BMW 8 Series planets left me with the keys to this car and the M850i Gran Coupe (also using the Carbon Core body) at the same time, and the difference between their softest settings is appreciable.

Also be aware that at 12.2m the M8 Gran Coupe’s turning circle is substantial, and it’s just as well all that camera, sensor and self-parking tech is available to help you guide this ship into port.

The M8’s electrically-assisted, variable-ratio steering features an ‘M’ specific calibration to deliver satisfying precision and good road feel. But in similar fashion to the ride a noticeable amount of unwelcome feedback comes through to the wheel.

The fat Pirelli P Zero rubber (275/35 fr / 285/35 rr) grips hard, and the monster brakes (ventilated all around, with 395mm rotors and six-piston calipers up front) wash off speed without fuss or fade.

But overall, you’ll have to live with a less refined drive when you sign on for the M8 Competition. Straight away it feels faster but lacks the M850i’s lighter touch. No matter which drive or suspension mode you select, responses are more aggressive and physical.

To fully explore and enjoy the M8 Competition’s abilities it feels like the race circuit is its most appropriate habitat. On the open road, the M850i is all the Gran Coupe you’re going to need.

Never have I met a car this powerful and superbly athletic that is as pleasurable to drive alone on great, fast roads as it is to pilot at 50km/h in the suburbs with a family on board.

It exceeds my understanding of engineering that something this large can move so quickly. That in an instant can turn and tip into a corner with such precision and effortlessness.

Yet it can switch seamlessly and happily to coping with speed bumps and potholes, delivering a ride so comfortable it'll send babies off to sleep. And it did.

The only issue, and this is such a tiny thing, is the dash-mounted gearshift, which means having to reach up and select Drive or Reverse or Park, which, when executing a three-point turn, is necessarily frustrating.

Still, I'm giving the Turbo GT a 10 out of 10 for driving under all conditions, and we didn't even go off-road, which of course you can do, as long as it's not too wild.

The Porsche Cayenne Turbo GT hasn't been locally crash tested and so doesn't have an ANCAP rating.

That's quite normal for super high-end cars. But, when this third-generation model first arrived in 2017 it was tested by ANCAP's European equivalent, Euro NCAP, and was awarded the maximum five stars.

There's AEB which operates at city, urban and highway speeds, and lane keeping assistance, and lane change assistance which is a form of blind-spot warning, and adaptive cruise control. You can option rear cross-traffic alert, as well.

A space saver spare wheel is under the boot floor.

BMW offers a three year/unlimited km warranty, which is at least a couple of years off the mainstream market pace, and lagging other premium players like Mercedes-Benz and Genesis, both sitting at five years/unlimited km.

Roadside assistance is included for the duration of the warranty period, and the standard ‘Concierge Service’ provides everything from flight information, to global weather updates, and restaurant recommendations, from a real human.

Technically, service is ‘condition based’ with the car telling you when it’s time to hit the workshop, but you can use every 12 months/15,000km as a guide.

BMW Australia offers ‘Service Inclusive’ packages that require customers to pre-pay for servicing, allowing the cost to be covered off in finance or leasing packages and reducing the need for concern about paying for maintenance further down the track.

BMW says there are different packages available, from three to 10 years, or between 40,000 and 200,000km.

The Cayenne Turbo GT is covered by Porsche's three-year, unlimited kilometre warranty, which is lagging behind in terms of duration even compared to other luxury brands such as Mercedes-Benz, which offers five years.

Servicing is recommended annually or every 15,000km, although there isn't a capped price maintenance plan with final costs determined at the dealer level (in line with variable labour rates by state or territory).