Audi RS Q8 vs Mercedes-Benz GLS-Class

What's the difference?

The Audi RS Q8 Performance is a lot - of everything. It offers lots of power, lots of performance, lots of space and lots of luxury. But it’s also a lot of money, and at more than $250k it’s not going to be on everyone’s shopping list. It’s a very niche proposition for a small group of buyers. For those select few, those who want a lot of everything and who crave the ultimate of whatever product they’re buying, then the RS Q8 Performance is going to be a very tempting proposition - even if they never set any lap record in it.

Note: CarsGuide attended this event as a guest of the manufacturer, with travel, accommodation and meals provided.

The GLS63 is an intimidating beast from afar, but it rewards its occupants in almost every way. Yep, there really isn’t a box it doesn’t tick without serious compromise, such is its breadth of capability.

If there was ever a Swiss Army Knife of cars, the GLS63 is definitely a contender for the title, one that makes it very hard to wipe the smile off your face. Just make sure you can fit it in your garage first…

We don’t refer to ‘facelifted’ cars for no reason, the RS Q8 Performance has a number of visual changes.

These include a new Audi ‘singleframe grille’ and new front bumper design, with a new Matt Carbon trim package available to highlight that.

There’s also a new rear bumper design as well as new digital daytime running lights at the front and digital OLED lights at the rear.

The unique forged alloy wheels are another design change, but also bring a functional element. Measuring 23 inches they do a good job of filling out the wheel arches and give the RS Q8 Performance a purposeful stance and good proportions. But they are also 5kg lighter per wheel than the 22-inch rims on the RS Q8, saving unsprung weight to help the ride and handling.

Inside, Audi hasn’t made any dramatic changes to the design, which is fine because the brand does some of the best cabins on the market in terms of look and feel.

What is new is an aluminium inlay and an optional RS interior design package which provides a unique finish to the seats, with contrasting stitching, for an additional $4100.

If the GLS63 was a Marvel superhero, it would undoubtedly be the Hulk. Simply put, it has road presence like few others. In fact, it’s frankly menacing.

Of course, the GLS is already pretty intimidating due to its sheer size and blocky design, but the GLS63’s full-fat AMG treatment takes it to another level.

Naturally, the GLS63 gets an aggressive body kit, with its purposeful bumpers, side skirts and rear spoiler serving as instant reminders of what you’re dealing with, but it’s AMG’s signature Panamericana grille insert that really hammers home the point.

Around the side, the GLS63’s 22-inch alloy wheels with staggered tyres (front: 275/50, rear: 315/45) make their presence known, positioned below the wheelarch extensions.

That said, some fun’s also had at the rear end, where the GLS63’s diffuser element integrates the foreboding sports exhaust system with quad tailpipes very neatly.

The focused Multibeam LED headlights also look the part, while the opposing LED tail-lights tie everything together outside quite nicely.

Inside, the GLS63 stands out from the GLS crowd with its sports steering wheel with Dinamica microfibre accents, and multi-contour front seats, which are covered in Nappa leather alongside the armrests, dashboard and door shoulders and inserts.

Of note, the doors bins are unfortunately of the hard plastic variety, which is very disappointing in a vehicle that costs this much. You would expect that cow hide would also been applied to them, but alas it isn’t.

The GLS63’s black headliner serves as an obligatory reminder of its sporting intent, and while it makes for a dark cabin, metallic accents are prominent throughout, while the optional trim (our test vehicle had carbon-fibre) mixes things up, alongside the ambient lighting.

And let’s not forget the GLS63 is still loaded with plenty of cutting-edge technology, including a pair of 12.3-inch displays, with one the central touchscreen and the other the digital instrument cluster.

Both are powered by Mercedes’ class-leading MBUX multimedia system and feature Apple CarPlay and Android Auto support. This set-up arguably remains the best there is today thanks to its speed and breadth of functionality and input methods.

While it’s easy to get swept up in the power and speed of the RS Q8 Performance, it’s important to remember that it’s an SUV and it needs to offer ‘utility’ as well as ‘sports’. 

With that in mind, the front seat occupants are well looked after with supportive and comfortable sports seats, with a good amount of small item storage spaces. 

The rear seats are surprisingly comfortable, despite the sloping roofline of this ‘coupe-style’ SUV. Audi has cut recesses into the ceiling to create more headroom, so it will be fine for anyone under six-foot tall. Despite there being five seat belts, this is realistically more of a four-seater for adults, although three smaller kids could squeeze across the back.

There’s also a pair of cupholders, two USB-C ports, a 12-volt outlet and your own climate controls for the rear passengers.

As for the boot, again it loses some volume because it’s not a wagon-style SUV, but there’s still a decent, square floor space with a claimed 605 litres of capacity.

So, overall the Q8 obviously isn’t the most practical version of an SUV, but it does well given its focus on style.

Measuring 5243mm, 2030mm wide and 1782mm tall with a 3135mm wheelbase, the GLS63 is an upper-large SUV in every sense of the term, which means it’s also very practical.

For example, cargo capacity below the load cover is decent, at 355L, but stow the 50/50 power-split-folding third row via the boot and it’s very good, at 890L, or drop the 40/20/40 power-split-folding middle bench, too, and it becomes a cavernous 2400L.

Better yet, the boot’s aperture is almost square, and its floor’s flat, while there’s no load lip to contend with, making loading bulkier items even easier. Up to four tie-down points are also on hand (depending on seating configuration) to secure loose cargo.

Under the false floor is the space-saver spare, which is to be expected, but what isn’t expected necessarily is the fact there’s also enough room there for the cargo cover when it’s not in use, which would be the case if six or more passengers are regularly onboard.

Moving into the power-sliding second row, the GLS63’s practicality is once again brought to the fore, with up to six-plus inches of legroom available behind my 184cm driving position.

There’s also two inches of headroom with the panoramic sunroof in situ, not to mention just enough toe-room. The GLS63’s small transmission tunnel and sheer width also mean three adults can be seated on the middle bench with few complaints.

Amenities-wise, the second row has map pockets on the front-seat backrest and a small fold-down cubby below the rear climate controls, with it containing two slots for smartphones and a pair of strategically placed USB-C ports.

The rear door bins can take one large bottle each, while a fold-down central armrest is also on hand, featuring a shallow tray and retractable (and flimsy) cupholders.

Alternatively, the $2800 Rear Seat Comfort Package fitted to our test vehicle subs in a tablet that can control the multimedia system, a wireless smartphone charger and a small cubby into the former, as well as a heated/cooled cupholder atop the rear of the centre console.

In the third row, it’s not quite as roomy if you’re an adult. With the middle bench in its most accommodating position, my knees still brush up against its backrest, which is to be expected given it’s primarily designed for children. I also have an inch of headroom there.

Nonetheless, getting in and out of the third row is relatively easy as the power-operated middle bench tumbles forward and provides just enough space to make entry and exit somewhat graceful.

When seated, rear occupants are treated to two USB-C ports and one small cupholder each, so they’re arguably taken better care of than those in the middle.

Child seats are well and truly accommodated, with four ISOFIX and five top-tether anchorage points fitted across the second and third rows, although the latter will inevitably prove to be a much tighter fit.

The driver and front passenger are still taken care of, with a front cubby taken up by two heated/cooled cupholders, a wireless smartphone charger, two USB-C ports and a 12V power outlet, while their door bins take one large and one small bottle each.

In-cabin storage options include the large central storage bin, which hides another USB-C port, while the glovebox is on the smaller side, with about a third of it taken up by the fragrance, which is pumped into the cabin to ensure the interior always smells its best.

Priced from $255,700 plus on-road costs, the GLS63 commands a $34,329 premium over its predecessor, although buyers are arguably getting more bang for their buck than before, even if it does sit well clear of the two other GLS variants: the $147,100 GLS450 and $153,900 GLS400d.

Standard equipment not already mentioned in the GLS63 includes regular metallic paintwork (our test vehicle was finished in Selenite Grey), dusk-sensing lights, rain-sensing wipers, power-folding side mirrors with heating, soft-close doors, roof rails, rear privacy glass and a power-operated tailgate.

Inside, keyless entry and start, augmented reality (AR) satellite navigation with live traffic, digital radio, a 590W Burmester surround-sound system with 13 speakers, a head-up display, a panoramic sunroof, heated seats (including middle outboard) and armrests, cooled front seats with massaging functionality, power-adjustable seats, a power-adjustable steering column, temperature-controlled front cupholders, five-zone climate control, stainless-steel pedals and an auto-dimming rearview mirror feature.

With BMW not offering an X7 M (although the slightly smaller $209,900 X5 M Competition is available) and the $208,500 Audi RS Q8 really from the segment below, the GLS63 does not have a direct rival in the Upper-large SUV segment.

In fact, the $334,700 Bentley Bentayga V8 is actually the model that comes closest to the GLS63 when looking for a seven-seater with a similar level of bent-eight performance.

This is the latest iteration of Audi’s twin-turbo 4.0-litre V8 petrol engine - and it’s a beauty.

While this engine is used in a variety of models, for the RS Q8 Performance Audi has taken power to 471kW with 850Nm of torque, which, as mentioned earlier, makes it the most powerful internal combustion engine Audi has ever offered in a production car.

That’s also a big boost over the previous RS Q8, which managed 441kW/800Nm, and is only just shy of the 485kW/850Nm offered by its ‘cousin’, the Porsche Cayenne Turbo GT.

Audi claims that the RS Q8 Performance will launch 0-100km/h in just 3.6 seconds and keep going to an electronically limited top speed of 250km/h. We tried to test the acceleration time on a closed circuit, but driving into a very strong headwind the big SUV could manage only 4.4 seconds - which is still a very quick time given its size and luxury.

The engine is paired to an eight-speed automatic transmission and Audi’s trademark quattro all-wheel-drive system to help smoothly transmit so much power to the road.

The GLS63 is powered by a familiar 4.0-litre twin-turbo V8 petrol engine, with its version producing a thumping 450kW of power at 5750rpm and 850Nm of torque from 2250-5000rpm.

This unit is mated to a nine-speed torque-converter automatic transmission and AMG’s fully variable 4Matic+ all-wheel-drive system with torque vectoring and a rear limited-slip differential.

This set-up also features Mercedes’ EQ Boost 48V mild-hybrid system, which actually gives a 16kW/250Nm electric boost in short bursts, such as when accelerating off the line.

Speaking of which, the GLS63 sprints from a standstill to 100km/h in just 4.2 seconds, while its top speed is electronically limited to 250km/h.
 

Unfortunately you don’t get the most powerful production engine without some trade-off, and for the RS Q8 Performance that means significant fuel consumption. The official fuel economy rating is a very thirsty 12.2L/100km, but that's the best-case scenario too. If you partake in some spirited driving that unleashes the full potential of the engine will result in a higher rate of premium unleaded being consumed by the big V8. We saw returns in the high teens across our time, but that was largely open road driving, so we’ll reserve final judgement for an extended test drive across more varied conditions.

Thankfully there’s a fairly large 85L fuel tank, so if you can hit the claimed average you can get a theoretical 696km of range.

The GLS63’s fuel consumption on the combined-cycle test (ADR 81/02) is 13.0L per 100km, while its carbon dioxide emissions are 296 grams per km. All things considered, both claims are unsurprisingly high.

In our real-world testing, we averaged a fearsome 18.5L/100km over 65km of driving, split between highways and country roads, so not your usual mix. A very heavy right foot definitely influenced that result, but don’t expect to do too much better in a normal run.

For reference, the GLS63’s 90L fuel tank can be filled up with 98RON petrol at a minimum.

Obviously the RS Q8 Performance is all about speed, Audi made its intention clear by sending it to the Nurburgring to set a new SUV lap record for an SUV. But the reality is most owners are unlikely to hit the racetrack in the RS Q8, so what’s it like on the road?

In a word? Impressive.

While the engine is undoubtedly the star attraction offering up so much effortless performance, the RS Q8 Performance wouldn’t be so quick around the Nurburgring or as nice to drive on the road without its highly advanced chassis systems.

It has an array of technology to help it handle, it has active air suspension, adaptive dampers, active roll stabilisation and all-wheel steering, which help to make this big SUV handle like a much smaller car.

The suspension does a remarkable job of providing a compliant ride on such large alloy wheels, while also providing responsiveness.

The handling is certainly helped by the all-wheel steering, which gets the rear wheels to turn in the opposite direction to the fronts at low speed (below 50km/h), but in the same direction at high speed (above 80km/h), making the big SUV feels much more direct when changing direction.

As for the overall experience, that’s helped by Audi’s surprising decision to actually remove some of the sound insulation, which allows you to hear the engine even more than you ordinarily would. This really plays to the dynamic nature of the RS Q8 Performance.

Frankly, the GLS63 has absolutely no right being as capable as it is. It’s a really big bus that’s legitimately convinced it’s a sports car half its size.

Being a GLS variant, the GLS63 has independent suspension consisting of four-link front and multi-link rear axles with air springs and adaptive dampers, but its party trick is the addition of active anti-roll bars.

In what feels like magic, the GLS63 is simply not intimidated by corners, despite having massive dimensions and a considerable 2555kg (kerb weight) to deal with.

The active anti-roll bars make the GLS63 so much easier to drive fast through the twisty stuff, almost eliminating body roll, taking one key variable out of the equation for the driver. Active engine mounts are also fitted, helping to settle things even further.

The electric power steering on hand is also good. It is speed-sensitive and has a variable ratio, which basically makes the set-up more direct when it needs to be. It’s typically light in hand, too, until one of the sportier drive modes is engaged and extra heft is added.

So, handling is scarcely believable, which means the ride must be compromised, right? Yes and no. With the adaptive dampers in their softest setting, the GLS63 is very compliant. In fact, we’d say it feels luxurious when compared to other high-performance SUVs.

That said, our test vehicle was fitted with the optional 23-inch alloy wheels ($3900), which look the part but expose sharp edges and other road imperfections, not to mention generate noise easily heard inside. Naturally, feedback is exacerbated in the sportier drive modes.

Anyway, there’s more performance, and the GLS63 has the rest in spades. Its engine is a powerhouse in every sense of the word. It’s so powerful, in fact, that it hilariously hunkers down off the line or when suddenly accelerating at low speed.

Thanks to the mild-hybrid system, wads of torque is available from the get-go, making for a highly responsive driving experience, even in those rare moments when the engine isn’t on song.

While not as characterful as some of the other members in the 63 series, the GLS63 still makes some thoroughly entertaining noises, with its sports exhaust system popping like mad while on the overrun.

All of this ability is very well and good, but you need to be able to pull up quickly, and the high-performance braking package (400mm front and 370mm rear discs with six-piston fixed callipers and single-pot floating stoppers respectively) mercifully does exactly that.

Neither ANCAP nor its European counterpart, Euro NCAP, have awarded the GLS range a safety rating, but it’s fair to assume it would perform well in testing.

Advanced driver-assist systems in the GLS63 extend to autonomous emergency braking with pedestrian and cyclist detection, lane-keep and steering assist (including emergency), adaptive cruise control, active blind-spot monitoring, rear cross-traffic alert, traffic sign recognition, driver attention alert, high-beam assist, tyre pressure monitoring, hill-descent control, hill-start assist, park assist, surround-view cameras and front and rear parking sensors.

Other standard safety equipment includes nine airbags (dual front, front-side, curtain and rear-side plus driver’s knee), anti-skid brakes (ABS), electronic brake-force distribution (EBD) and the usual electronic stability and traction control systems. Yep, it doesn’t leave much to be desired on the safety front.

Despite the extra power and fancy new brakes, the RS Q8 Performance costs the same to service as the existing RS Q8.

That means $4690 for Audi’s five-year service plan, and $5720 for the Audi Advantage.

The latter package includes an extra two-year, unlimited kilometre warranty on top of Audi’s five year/unlimited km coverage. It also includes two extra services and two more years of roadside assistance, to keep you covered for seven years total.

That’s good, but it’s still an extra cost when many mainstream brands already offer seven years of coverage as standard.

As with all Mercedes-AMG models, the GLS63 comes with a five-year/unlimited-kilometre warranty, which currently sets the standard for the premium market. It also comes with five years of roadside assistance.

The GLS63’s service intervals are relatively long, at every 12 months or 20,000km (whichever comes first). Better yet, it’s available with a five-year/100,000km capped-price servicing plan, but it costs $4450.