2018 Audi A8 vs Mercedes-Benz S-Class

What's the difference?

The new A8 is a very accomplished machine, and can certainly be optioned up with enough toys to entertain and comfort whether you're riding in the front or back.

It's not possible to say if its better than the S-Class or 7 Series in isolation, but it has a unique design ambience that's unmistakably Audi. If you're a four-ring devotee, you won't be missing out.

Based on this test, the sweet spot of the range is the long-wheelbase 55 TFSI. At this end of the market, it's fair to say the extra $12,000 for the added length and $3000 for the smoothest and most powerful engine are worth it.

Regardless of the bigger wheels, we'd probably spring for the Premium plus package and the Executive package's rear seat with the Entertainment package for all the most impressive toys. This would mean a total list of almost $250k, but it's arguably how Audi intended the new model to be.

Both of these vast vehicles are phenomenally comfortable - this is the kind of car that Mercedes does so well, and has done for decades. The S Class is rarely a disappointment but it's difficult to believe that such a big, heavy GT car can also dance the way the S63 does.

The S560 is far more weighted to being a GT - supremely comfortable with that active suspension, a growly, refined V8 and a cabin full of gadgets and comfort. The S63 is altogether more aggressive, to look at and to drive. Lopping the roof off both of them adds weight but, like any cruiser, also puts you out in the sun, the breeze and into your surroundings. Plus, in the case of the S63, you get more exhaust noise.

They're two very different cars and not just because of the engine. After all these years admiring it from afar, the S63 has delivered on my teenage expectations - fast, smooth and utterly mad.

At first glance the new A8's exterior styling may look a tad obvious, with unmistakably Audi design adding a bunch of straight lines to make things look more serious. 

The reality is far more considered, being the first whole design to emerge under Audi Design boss Marc Lichte's stewardship. Previewed by the first Prologue concept in 2014, the result has an elegance that underlines its position as Audi's flagship and is less likely to be confused with an A6 than the S-Class can be with the E-Class.

If you're after the ultimate in design details and lighting performance, you can also opt for $13,200 laser headlights that can double the range of LED headlights to 600m ahead. This option also brings OLED tail-lights with jewel-like filaments less than 1.0mm thick. 

Compared with the third-generation model it replaces, the size of the new A8 is 37mm longer, 13mm taller but 4.0mm narrower, riding on a 6.0mm longer (2998mm) wheelbase. The long wheelbase version is 130mm longer again in wheelbase and overall. 

It rides on the latest MLBevo architecture shared with the A4, A5, A6, A7, Q5 and Q7, along with the Bentley Bentayga, new Porsche Cayenne and VW Touareg, and the upcoming Q8. 

In A8 guise, it combines aluminium, steel, magnesium and CFRP to result in the biggest material variety used in an Audi to date. Kerb weight ranges from 1995kg for the short-wheelbase petrol model to 2020kg for the long-wheelbase version, with the diesel versions adding 55kg respectively.

A 15-spoke, 19-inch wheel design is standard for Australia, but the Premium plus package fitted to all the cars we tested brings a 10-spoke 20-inch design, while the options list includes another three choices of 20-inch wheels. You can also get 21-inch alloys with the optional Sport package.

As you'll see in the interior images, the A8 represents another significant step forward for Audi design, with horizontal themes and numerous traditional controls now hidden beneath touchpads.

Key among these is the deletion of the centre console controller for the multimedia system, which has been replaced by an 8.6-inch secondary touchscreen beneath the 10.1-inch main screen. Apple CarPlay and Android Auto smartphone interfaces are available via USB connection, and the A8 will act as a mobile Wi-Fi hotspot if you sign up for a data plan.

This split layout is less imposing than using one giant screen as in a Tesla, and both give haptic and acoustic feedback to commands to simplify use while driving. All versions also score the excellent 12.3-inch 'Virtual Cockpit' display ahead of the driver. 

All A8s also now get a smartphone-like back seat remote controller, which enables control of temperature settings, seat adjustment, lighting, media functions and window blinds (when optioned) via its 5.7-inch OLED touchscreen.

Another surprise detail is that the interior door handles are now power assisted, which represents the lengths Audi has gone to in reducing control weights.

The S Class Coupe is obviously related to the sedan but manages a svelte appearance. Slimmer hipped and with a more Coke-bottle shape, the Coupe - if you squint a bit - has a bit of the classic old pagoda about it. Obviously you can't do pillars that slim anymore, but the glass roof takes away some of the visual weight inside and out. 

The cabriolet's roof is nicely integrated and looks good when it's  up, which isn't always the case.

They all look long, though. It's obvious to see why the cars all run on 20-inch wheels - anything smaller would look hilarious.

The cabin is a fairly sensible re-imagining of the E-Class. The big twin-screen layout of the dash and multimedia system seems a bit more at home here. The chintzy Burmester speakers in the doors let down an otherwise classy cabin, which steers clear of otiose vulgarity in looks and materials.

Choosing the biggest sedan in the line-up isn't just about outdoing your neighbours, it's also fair to expect enough room to stretch out and ponder your stock options. 

Despite the new A8's minor 6.0mm wheelbase growth, the interior dimensions have grown 32mm in length, which has expanded legroom as well as headroom.

Fundamental practicality elements are covered as well, with a cupholder and bottle holder for each outboard passenger, an array of USB and 12-volt charge points and two ISOFIX child seat mounts for the back seat. There's also a Qi wireless phone charger within the centre console. 

Boot space is a useful 505 litres, and while there's no split-fold for the back seat, there is the capacity to bring curtain rods home from Bunnings via the ski port.  There is also a space saver spare wheel beneath the boot floor. 

Well look, if you end up in the back of the S Coupe, it's not a riot of space. Obviously it has back seats (the SL doesn't even squeeze a jump seat into its considerable length) but they're for occasional, if luxurious, use.

The boot is a reasonably decent 400 litres, obviously the cabriolet loses a few litres with the roof folded. Front and rear passengers will both enjoy a pair of cupholders and the whopping long doors will each hold a bottle.

One thing hasn't changed in nearly 20 years - the S isn't cheap. Available in coupe and cabriolet, the S560 starts at $314,900 for the former and $336,900 for the latter. Step up to the S63 pair and you'll pay from $370,500 for the coupe and $399,900 for the cab. If you're super keen for something spectacular, the twin-turbo V12-powered S65 is available for between $508,900 and $520,500, and features Swarovski crystals in the headlights, for some reason.

As you can imagine, there's quite a bit to cover, so for both cars I'll stick to the edited highlights. The S560s roll on 20-inch alloys, has a 590-watt 13 speaker sound system, digital TV, auto parking, active cruise control, panoramic glass roof, Nappa leather, active seats and power-closing doors.

It also comes standard with a heating pack that not only heats the seats but the steering wheel and centre console. In the cabriolet you also get the 'Airscarf' neck heater.

Both cars also feature's Mercedes' Magic Body Control with curve function. More of that wacky feature later.

The S63 AMG is a step up in power, price and spec. One notable change from the S560 is the loss of 'Magic Body Control', which is replaced with mere air suspension. The 20-inch alloys are 10-spoke forged units, the brakes higher performance composites with red calipers, while an AMG sports exhaust brings the noise.

Naturally, both are swathed in high-quality leather and feature dual-zone climate control, heated and cooled electric seats that adjust in every direction, deep carpets, keyless entry and start, fully digital dashboards and just about every gadget to which you can point your imagination.

Entertainment and sat nav are via Mercedes' 'Comand' system, which is displayed on a massive 12.3-inch slab of glass at the top of the dashboard. The 13-speaker Burmester-branded system is predictably impressive and with Apple CarPlay and Android Auto, you only have to use the basic software for the radio or various car controls.

You might be surprised to learn there's no V8 in the new A8's arsenal - for now, the S8 could change that - but an even greater sign of the times is the return of a petrol version for the first time since 2013. Efficiency gains are the main reason for the petrol comeback, which is explained in detail under the fuel consumption heading below.

Both the 210kW/600Nm 50 TDI turbo-diesel and 250kW/500Nm 55 TFSI petrol specifications use 3.0-litre turbocharged V6s which may seem to be simply plucked from existing models, but they bring mild hybrid technology to the Audi line-up for the first time. 

Unlike conventional hybrids that use an electric motor to provide horsepower to drive the vehicle, a mild hybrid (or MHEV) enables the combustion engine to be switched off when the vehicle is coasting or braking, or effectively as an extension of a start/stop system which conserves fuel when a car is stationary.

The A8's mild hybrid system is facilitated by the move to a 48 volt electrical system, with a supplementary 10Ah lithium-ion battery mounted in the boot to keep the electrical systems fed for up to 40 seconds with the engine switched off. Audi claims the system has the capacity to save up to 0.7L/100km.

An extra starter motor has been integrated with the alternator to restart the engine more smoothly via a belt, rather than the conventional cog and ring gear used by the dedicated starter motor for cold starts.

Both engine specs deliver their max torque rating from just above idle, with the 50 TDI at 1250rpm and the 55 TSFI at 1370. Claimed 0-100km/h acceleration performance figures are an impressive 5.9s and 5.6s respectively.

Like all recent longitudinal-engined Audis, the new A8 uses a version of ZF's much lauded eight-speed torque converter auto gearbox, and both engines send power to all four wheels via the 'quattro' all-wheel drive system. 

The optional all-wheel steer system can twist the rear wheels by as much as five degrees, reducing the turning circle by around 1.0m at slow speeds. While at higher speeds, the rear wheels move parallel with the fronts by as much as two degrees to improve stability, particularly for rapid lane changes and evasive manoeuvres. 

All new A8 variants carry a maximum braked towing capacity of 2300kg.

All four coupes and cabriolets ship with Daimler's formidable 4.0-litre twin-turbo V8. The S560 scores 345kW/700Nm to drive the rear wheels through Benz's own nine-speed automatic. With all of that available, the S560 will crack the ton in 4.6 seconds and make a wonderful racket on the way.

Moving on to the S63, the same engine delivers a massive 450kW/900Nm. The run from 0-100km/h is dispatched in just 3.5 seconds and if I thought the S560 made a good noise, the S63 with its standard sports exhaust makes a better one. Again, Mercedes' nine-speeder is along for the ride.

Gone are the days where full-size luxury sedans got away with devil-may-care fuel consumption, and even though they still spin six cylinders and need to move around two tonnes, the 55 TFSI petrol versions manage an 8.2L/100km official combined figure. This is when using at least 95 RON Premium unleaded of course. 

As you'd expect, the diesel fuel economy is even better with 5.9-6.0 official figures across wheelbases.

With a fuel tank capacity of 72 litres, this suggests a theoretical range between fills of 878km for the petrol models, and between 1200-1220km for the diesels. The A8's spec sheet lists the option of an 82-litre tank if they aren't quite far enough for you.

The lower-powered 560 drinks 98RON at the rate of 8.5L/100km for the coupe and 9.9L/100km for the heavier cabriolet.

The S63 ups the ante with 9.9L/100km for the coupe and an identical 9.9L/100km for the cab.

Our launch program contained some...er...spirited driving, which would explain the mid to high-teens fuel figures.

Our test started in the worst of Sydney morning traffic, which presented the chance to put the latest adaptive cruise assist (ACA) system through its paces on a very clogged Eastern Distributor. 

I'm a huge fan of active cruise control systems that guide the vehicle from speed to a stop, but the A8's ability to start moving again is another step beyond. It helps you avoid being ‘that guy' who hasn't noticed the traffic moving, and would no doubt work wonders for traffic flow if all cars were so equipped. Given the chance, Audi says this system works all the way from 0-250km/h.  

No matter what your reaction to the A8's exterior, the freshness of the interior design is like no other, and everything you touch feels first class. 

The four-spoke steering wheel has a surprisingly large diameter and is shared with the upcoming A6, but uses thinner spokes than the norm to promote visibility of the virtual cockpit display as the wheel is twirled.

The haptic and acoustic screens make it as easy as we've experienced to handle a touchscreen while driving, but not quite as simple as the previous console controller. 

Front and rear seats are softly padded for comfort rather than support, and unsurprisingly there's ample room in every direction for this 172cm tester, regardless of wheelbase.

All examples of the A8 we drove were optioned with the Premium plus package, which means one inch larger 20-inch alloys. Despite all A8s coming standard with adaptive air suspension, small bumps like cats eyes and expansion joints are more noticeable than you might expect. As is often the case, the standard 19-inch alloy wheels are likely to be the solution.

We drove both engines and wheelbase choices at the A8 launch event, and you need to be paying close attention to hear any extra noise from the diesel. It does make a muted groan under throttle, but likely worth the 300-plus kilometres of extra range if that's what you're after. 

The diesel's smoothness is also no doubt aided by its use of active engine mounts. If you're after outright refinement and performance, the petrol is the one for you but neither feel in any way sluggish. 

Heading through the bends of the Royal National Park and then back over the hills via Macquarie Pass at pace, there was no disguising the fact that the A8 is a big car, and it tends to float unless you select 'Dynamic' from the drive mode selector. Regardless of mode, it's more planted than any luxury SUV.  

Making a bee-line back to Sydney via the Hume, the A8 simply wafted along at 110km/h in near silence. As you'd expect.

Let's start with the S560. That smooth V8 rumble is all you'll ever hear if you just slot into drive and go for a leisurely spin. The nine-speed automatic continues to be a revelation to me - in the GLC63 it's good and here, once again, it's excellent, finding the right gear for the occasion and riding the fat torque curve. Other nine-speed autos are not very good at all.

The test route for the S560 played to the strengths of the car. It had some lovely winding roads, which brought the trick suspension into focus - the Magic Body Control with curve function is hilarious. While the active suspension works hard at all times to ensure the ride is smooth and drama free, the Curve mode (no, really) actually leans the car into corners.

Those of you who remember the video game Wipeout 2097 will be big fans of Curve mode. As you approach a corner, you turn the wheel and then the car leans into the bend. This isn't active damping reading the road, it's the outside suspension lifting the car and the inside lowering it, so the car feels like it's gliding, like a hovercar. It's wild but oddly calming. Mercedes reckons it's great for those who get car sick. As I didn't have my wife on hand to test this theory - she chucks at the first sign of a corner - I couldn't verify this claim. That will have to wait.

The S63 AMG is a completely different proposition. The air suspension is more than up to the job of helping smother the effects of the car's considerable weight, meaning that no matter what you're up to, the car feels reasonably light on its feet. It never feels small, though, commanding the respect of the driver and plenty of space from other road users.

And boy, do you need some space if you kick the S63 into Sport mode. In true AMG style, the electronic reins relax and the big luxury coupe cheerfully kicks off. The tail will wriggle under an unsympathetic right foot, that signature V8 roar, crackle and hiss filling your ears. The S63 is always the harder-feeling car, but it delivers with a more sporting drive than the S560.

Being the generous soul I am, I volunteered to return the S63 to its home for the evening rather than consign it to the back of a truck. On the back roads I took to reach the highway, it was rock solid - fast, predictable and a lot of fun. Once I found the boring straight bits, it turned into a supremely comfortable cruiser, ticking along in ninth at the legal limit (and being Melbourne, it was very much the legal limit), dispatching overtaking with barely a flex of a toe. 

The active cruise took the stress of keeping away from the State Revenue Office's clutches while being quiet and utterly pleasant.

The S-Class coupe comes loaded with eight airbags, ABS, stability and traction controls, forward and reverse AEB with pedestrian detection, reversing camera, crosswind assist (I know, right?), traffic-sign recognition and reverse cross traffic alert.

The S-Class Coupe does not have an ANCAP or EuroNCAP rating.

Like all Audis, the new A8 is covered by a three year, unlimited kilometre warranty. This is short of the five year-plus periods becoming more common among mainstream brands, but equal to the terms offered by BMW and Mercedes-Benz. Lexus differs by offering a four year, 100,000km plan.

Service intervals and capped price servicing mirror the previous A8, with a 12 month/15,000km schedule, and maintenance costs for the first three services can be wrapped into a package for $1900. 

We had no issues during our test, but any common faults, common problems or reliability issues are likely to appear on our A8 problems page.

Mercedes offers a three-year/unlimited-kilometre warranty with roadside assist for the duration.

The company also offers both service plans (where you pay up-front as part of the vehicle purchase) and capped-price servicing on the coupes. Servicing over three years is in the order $2500.