Mercedes-Benz Gls450 vs Audi S8

What's the difference?

The GLS450d impresses as an entry-level grade, as it’s a more family-friendly allrounder than the specialised AMG and Maybach variants. Its combination of a torque-rich diesel 48V hybrid drivetrain, air-cushioned suspension and plush interior are as well suited to luxury urban travel as they are to grand touring, where its heavy towing and generous load-carrying capabilities can shine. Whether it’s worth around $200K drive-away, only those who shop at the top end of town can decide.

The S8's existence is a source of joy for me because it's not a huge SUV. Yes, it's a huge sedan but it's a reminder that the technological flagship is alive and well, at least in Germany. And the important thing about these cars is the way the toys filter down through the rest of the range. That used to take years but we're seeing this cool stuff a lot more quickly, right down to the A1.

The S8 punches, and punches hard in this rarefied part of an already shrunken section of the market - the twin-turbo V8 matches its German rivals, it's lighter and it's as well-stacked as any of the three. What it doesn't do, however, is shout about itself the way the other two do.  It's the incognito choice.

This is an imposing vehicle in extravagant S-Class tradition, riding on an expansive 3135mm wheelbase and stretching more than 5.2 metres (5215mm) long and more than 2.0 metres (2030mm) wide with a turning circle that's nudging 13 metres.

However, it’s just under 1.8 metres (1798mm) tall, so there’s no clearance issues when accessing multi-storey carparks. And with its side-steps (or ‘running boards’ in nostalgic Benz speak) most adults can step rather than climb aboard, although passengers of shorter stature during our test noted that assist handles on the A and B pillars would be handy.

Central to its sophisticated chassis design is adaptive air suspension, which uses a pneumatic or ‘airbag’ form of springing with adaptive damping to continuously optimise ride comfort and handling response according to road conditions and driving dynamics (see Driving).

The GLS’s styling is clean and uncluttered with tasteful restraint evident in its chrome and satin-chrome highlights, yet it projects a majestic quality with its prominent four-louvre grille and elegantly spoked alloy wheels.

The spacious and sumptuous seven-seat interior is visually pleasing and practical, with a subtle blend of surface treatments, contrasting tones, lots of soft-touch surfaces and exposed stitching. This is combined (thankfully) with physical dials, switches and ‘piano key’ buttons to control numerous interior functions, in preference to distracting touchscreen prompts.

The sheetmetal is obviously very restrained given it's an Audi first, and secondly, it's just not done to go wild in this part of the market.

It's an A6 that's joined a gym, but didn't join that weird gym with men that can't run after you when you insult them (don't ask how I know this). Rolling on 21-inch wheels as standard, you can go up to massive 22s if you so choose.

The A8 created a subtle redirection of Audi's passenger car look, with the updated A4 and A6 both picking up on the horizontal bar between the rear lights and the huge grille framed by family lights with signature DRL patterns. The S8 builds on that with subtle S cues but nothing even vaguely shouty.

The interior acreage - or 'cabin', if you will - is very comfortable, but you already knew that. The multi-screen layout was first seen in the A8 and has now found its way into A7, Q8 and Q7 and is, as ever, brilliant to look at and use.

The MMI updates that have found their way into other cars are present and correct. Like the exterior, it's very restrained but not to the point of sparse minimalism, despite the lack of switches and buttons.

I really don't like the steering wheel, though, and I can't put my finger on why. It certainly isn't especially sporty-looking but I wonder if the standard flat-bottomed S wheel just looked stupid.

The materials are beautiful and everything fits together perfectly.

Although it has a hefty 2655kg kerb weight, our test vehicle’s 3420kg GVM rating provides a useful 765kg of load capacity, which should comfortably absorb the combined weight of up to seven occupants and light luggage. Or with the third row of seating folded, five occupants and heavier luggage.

It’s also rated to tow up to 3500kg of braked trailer and with its sizeable 6920kg GCM (or how much weight it can legally carry and tow at the same time) it can carry its maximum load while towing its maximum trailer weight.

So, that’s commendable practicality, given it would be well suited to owners that need to tow large caravans, boat trailers, horse floats etc in style without having to compromise much (if at all) on either passenger numbers or luggage capacity.

Driver and front passenger space and comfort is exceptional, as you’d expect. Storage includes a large glovebox plus a bottle holder and bin in each door. The front of the centre console has two USB-C ports, wireless phone charging and heated cupholders, while the rear of the console has a large storage box with a third USB-C port and padded lid that doubles as a comfy elbow rest.

Even tall passengers in the second row of seating enjoy spacious comfort, given I’m 186cm and with the driver’s seat set in my position I have ample knee clearance, foot room and head space.

However, the central passenger must contend with a transmission tunnel in the floor and shoulder room would be squeezy for three large adults, which is okay for short trips but a maximum of two would be ideal for longer journeys.

The rear of the centre console also treats second-row passengers to a pair of USB-C ports, adjustable air-vents and a control panel that allows independent climate adjustment.

There’s also a large bin/bottle holder in each door plus storage nets on each front seat backrest. The centre seat backrest folds flat to allow long items (skis etc) to slot between the outer backrests. And it also serves as a fold-down armrest, containing two cupholders and a lidded slimline compartment that’s ideal for hidden phone storage.

The third row is uncommonly spacious, even for tall people, with padded armrests on each side containing cup holders and twin USB-C ports.

The carpeted rear luggage area has four load-anchorage points, a first aid kit and 12v socket. With the third-row seats upright it offers 355 litres of load volume, which increases to 1350 litres with the third row folded and 2400 litres (or 2.4 cubic metres) with both the second and third rows folded.

The cabin is clearly built with rear seat passengers in mind, with rear leg and headroom configured for those continent-crossing drives.

The S8 has plenty of comfort for two rear seat passengers and a few amusing options to while away the hours in traffic or on the autobahn.

That doesn't mean the front seat passengers are in purgatory, with huge but supportive seats adjustable in all conceivable directions.

Front and rear rows score a pair of cupholders and bottle holders while the boot is a handy, if not awe-inspiring, 505 litres.

For $260,000 there is a lot to get through, as there is on the less sporty A8. Start with huge 21-inch alloys, 17-speaker Bang & Olufsen stereo, panoramic sunroof, matrix LED headlights with laser lights, soft-close doors, acoustic glazing, leather trim, S front seats, extra leather over the A8, Alcantara headlining, carbon inlays, four-zone climate control, heated and cooled front seats, 'Virtual Cockpit' with S mode, and a tyre repair kit.

You also get active suspension, a sport version of the 'quattro' all-wheel drive system (with a sport differential), and a walloping great twin-turbo V8 to get you moving.

A massive touchscreen on the centre stack (familiar in Q8, A7 and Q7) hosts Audi's 'MMI plus' system, which is very good and does away with the console-mounted rotary controller. It also has wireless Apple CarPlay to go with the console-bin wireless charging pad. Android Auto is still USB. 'Audi Connect plus', now in full-featured glory, is also along for the ride.

Another technical highlight is the active noise cancelling which is meant to reduce the noise in the cabin the same way noise cancelling headphones do.

There's a clever rear seat remote control, which is a little detachable tablet to allow those who are being chauffered to faff around with various settings.

Our car had the $13,900 'Sensory Package', which adds a 1820-watt B&O 3D sound system with 23 speakers, electrically adjustable outer rear seats along with heating, cooling and massage function, and full leather.

The GLS450d comes standard with a 3.0-litre turbocharged inline six-cylinder diesel producing 270kW of power at 4000rpm and 750Nm of torque between 1350-2800rpm.

This is paired with a 48V mild-hybrid system comprising a 48-volt battery (charged by regenerative braking) and an integrated starter-generator which provides both seamless engine stop-start and up to 15kW/200Nm of extra power and torque during acceleration.

A nine-speed torque converter automatic provides the choice of manual shifting using the steering wheel-mounted paddles, along with several selectable drive modes.

The active all-wheel-drive system continuously adjusts the engine’s torque delivery between front and rear axles (and individual wheels as needed) to maintain optimum traction and handling.

Under that long bonnet is a 4.0-litre twin-turbo V8 pumping out 420kW and a diesel-like 800Nm of torque. 

That's a lot, even for this big bruiser. Obviously, being an Audi S-car, it has quattro all-wheel drive, which is fed by an eight-speed ZF automatic. Which is in everything now. Well, just about.

That huge torque figure is available between 2000rpm and 4500rpm while peak power arrives at 6000rpm. The 0-100km/h sprint is despatched in - gulp - 3.8 seconds.

As it's riding on the MLB platform, the mild hybrid system is a 48-volt set-up. A lithium-ion battery in the boot takes charge from the belt alternator/starter, which means the S8 can coast at higher speeds with the engine off and also cut out at 22km/h and under in traffic.

The system can also add up to 60Nm of torque in the right conditions for up to six seconds, and if it happened for me, I didn't notice it.

Mercedes-Benz claims official combined consumption of 7.8L/100km and the dash display was showing 9.0 when we stopped to refuel at the completion of our 368km test, which included the usual mix of suburban, city and highway driving with up to five passengers at times and light luggage.

Our own figure, calculated from fuel bowser and tripmeter readings, was close at 9.5 which is outstanding sub-10L/100km economy for such a substantial vehicle in mostly metropolitan use. Therefore, based on our own consumption figure, you could expect a real-world driving range of around 950km from its 90-litre diesel tank.

The 10.5L/100km official figure is, shall we say, optimistic. The launch drive was mostly highway so there's no real information to be gleaned from that, so we'll have to wait for real world fuel figures.

I'd say 12-13L/100km is achievable if you don't like having fun, in which case, the lesser A8 is probably for you.

Audi says the MHEV system saves 0.8L/100km with an early cut-out for the stop-start and the ability to coast on the highway for over half a minute at a time.

It’s an enjoyable vehicle to drive, with multiple power adjustments for the seat and steering wheel combined with a large left footrest which provide supreme driver comfort and support.

The powerful and responsive turbocharged six-cylinder diesel and nine-speed auto are well suited to this application. The engine’s ample torque provides spirited acceleration from standing starts, taking only six seconds to reach triple-digit speeds.

This drivetrain would be well suited to heavy towing duties, given the 48V mild-hybrid system can contribute an extra 200Nm (in addition to the engine’s 750Nm), which raises the total theoretical torque output to almost 1000Nm.

The active air suspension provides a wonderfully cushioned ride that floats over bumpy roads, while maintaining excellent handling response and surprising agility. These commendable chassis dynamics, combined with the powerful and responsive drivetrain, makes the vehicle feel smaller and lighter than its dimensions and kerb weight would suggest.

Overall, it’s difficult to fault from a driver’s perspective, with the only exception being the voice activation function. This is often triggered by words or phrases other than ‘Hey Mercedes’ resulting in regular interruption of conversations. This needs some fine tuning.

Driving any of the cars in this segment is a rare treat, whether it's the 'entry level' diesel or this top of the heap sports sedan. My day with the S8 was filled with the usual surprise and delight that only these tech-packed cars can deliver.

Heading out of the Sydney CBD in 'Comfort' mode, the car scans the road ahead and adjusts the active suspension accordingly. You already know it has active suspension because when you pull the door handle, the car lifts by 50mm to make it a bit easier to get in.

The suspension's party trick is flat-topped speed bumps - drive at one, brake a little and sense the way the body feels like it stays exactly where it is in the air but the suspension almost completely flattens the speed hump.

It's uncanny and almost unnatural, with just the tiniest change in altitude and no noise from the suspension.

It also manages the terrible narrow lanes of CBD thoroughfares with ease, the lane keep system letting you know if you're straying.

On to the motorway and you get a feel for its crushing performance. You won't hear much, though - the stereo's noise-cancelling system shuts out almost all tyre noise and consistent wind noise is largely banished, too.

I'm going to admit I gasped when I found some corners. Active suspension bodes well for the tricky stuff, as does the all-wheel steering. Both are exceptionally clever systems for making the car feel a lot smaller in town and in car parks but they're also really good if you want some fun.

But the way the rear-wheel steer adds agility to such a big car is hilarious and clever. While you can't quite chuck it around - and really, you're not buying an A8-sized car for that kind of nonsense - brisk progress is far from intimidating.

Now, obviously, a Ford Fiesta would drive away from the S8 in the really tight stuff but it would take some time to properly shake it. The colossal torque from the V8 hurls even this two-tonne-plus limo out of the corners in a most satisfactory manner.

It's surprisingly agile for a machine more than five metres long and two metres wide. If your passengers are corner enthusiasts, you'll all be having fun in near silence. It's oddly engaging to be moving at pace in such a hushed cabin.

The S8's considerable safety equipment list includes nine airbags, ABS, stability and traction controls, forward AEB (up to 250km/h), reverse cross-traffic alert, lane departure warning, various collision mitigation and protection systems, exit warning, lane keep assist, active cruise control and on, and on, and on.

The rear seat's centre airbag is terribly clever, popping up between passengers to stop you knocking heads. Another clever trick is the way the car detects a side impact is about to happen, boosting the height of the side about to cop it to try and get the sills to take more of the impact, rather than the door.

Given the relatively niche status of the A8, let alone the S8, there is no ANCAP crash test or safety rating. One imagines given the ton of safety gear a five star rating is all but assured. Even the US IIHS gave the A8 a miss.

The GLS comes with a five-years/unlimited km warranty (better than BMW and Lexus) and five years of roadside assistance. Scheduled servicing is every 12 months/25,000km whichever occurs first.

Mercedes-Benz offers capped-price pre-paid servicing packages with three, four or five-year terms. For example, the total upfront cost of the minimum three-year term is $4090, or an average of $1363 per service.

Audi continues to fail to match Mercedes move to a five year warranty, sticking with three year/unlimited kilometre cover. BMW is still doing it too, so maybe Ingolstadt and Munich are playing chicken. 

You can get a five-year service plan for the S8, coming out at $3990 for the duration.