Audi A8 vs Mercedes-Benz S400

What's the difference?

The Audi A8 swims in a luxury car shark tank where those paying the big dollars expect top-shelf everything. It delivers a serene driving experience whether you’re in the front or the back, in a superbly engineered and executed luxury sedan package. Not perfect, but very, very impressive.

The 2018 Mercedes-Benz S-Class remains a technological tour de force, a luxury sedan to be reckoned with - one that has safety, technology, comfort, finesse and performance all rolled into a stylish package. 

It's hard to see why you'd need anything more than the S 350 d, which is now much more attractively priced. It'd be my pick, but I'd have to get the Energizing Comfort Control package, and probably the AMG styling pack, too. And even then it would cost less than its predecessor.

The A8 is close to 5.2 metres long, yet instantly recognisable as an Audi thanks mainly to its evenly weighted proportions, gently curved roofline and overall high-waisted design. Worth noting its drag coefficient (Cd) is an impressively slippery 0.25.

The characteristic look is accentuated by the brand’s signature, six-sided grille, in this instance highlighted by a matrix of high-relief chrome accents. And typically angular LED Matrix headlights sit either side.

Check out our video review for the carefully orchestrated animation they run through when the car is unlocked.

The car looks equally svelte and contemporary from the rear, with just the right amount of chrome lifting the tone and multi-spoke 20-inch rims filling the wheel arches nicely.

As you’d expect, the top-shelf look and feel continues inside with the seats trimmed in aniline leather, perforated on the front and outer rear positions, with genuine hide also covering the centre console, door rails and armrests, steering wheel and upper dashboard.

Fine grain ash wood inserts sit alongside brushed metal elements and a meticulous attention to detail is obvious… everywhere.

For example, the interior door handle design has been thoroughly thought through, requiring a simple underhand tap to open the door, rather than the more conventional, and ergonomically convoluted, ‘over the top’ movement.

Three sleek screens dial up the tech - a 10.1-inch multimedia interface at the top of the centre stack, an 8.6-inch display below it for heating and ventilation, and a 12.3-inch version of Audi’s ‘Virtual Cockpit’ in the instrument binnacle.

And the spacious rear is the epitome of cool, calm Teutonic form and function. You feel relaxed the moment you get in, and isn’t that the primary aim of a car like this?

I swear it has been facelifted, and the changes are bigger than they might appear. There is no doubt that the S-Class shape is largely unchanged, but the German company has kept the modifications minimal in the scheme of things.

That doesn’t mean those changes are unnecessary, though. The new headlights, for example, are standard on every model, and are constructed with 84 LEDs (including three for the daytime running lights), and of course they’re adaptive with automated high-beam - meaning they’ll shield other road users from the glare of the lights at night. And the lights themselves will throw a main beam up to 650 metres, according to the company. 

Other things are slightly more cosmetic, like the revised three-bar grille treatment, new front and rear bumper designs that feature broader sculpted sections to widen the stance of the car, and there are new LED tail-lights as well.

The smallest set of wheels used to consist of 18-inch rims, but now the base car rolls on 19s, while the rest of the expansive range sits on 20s. 

The inside has seen some changes, too, but the appearance of things in the cabin isn’t the focal point - its the usability of the technology that's the big change. 

Oh, but I should tell you there are now 64 ambient lighting colours to choose from, which is up from seven, and now you can also set the lighting in three different zones - so theoretically you can have blue, orange and green areas of the cockpit, if you’re gross.

Space is luxury, be it a large house, a first class seat or a spacious car, and at nearly 5.2 metres long with a close to 3.0m wheelbase the Audi A8 measures up. 

Even before you get in, the doors have an amazing sense of solidity and quality. It’s like opening and closing a bank vault… if that huge circular door had a power-assisted soft-close function. 

There’s copious amounts of space for the driver and front passenger with lots of storage including a lidded box between the front seats, complete with a two-piece longitudinally split top design, so you can sneak your half’s open without displacing your neighbour’s elbow.

The door bins are decent but there isn’t a specific cut-out for bottles, so it’s more a case of laying them down than standing them up. There’s also a handy covered cubby at the end of the door armrests.   

The glove box is a good size and there are two cupholders under a pop-up cover in the centre console.

Of course, the back is where space really counts, and there’s as much room as you’d find in, well… a limo.

Sitting behind the driver’s seat, set for my 183cm position, I enjoyed copious amounts of head, shoulder and legroom. 

There are electric sunblinds for the rear and rear side windows, controlled by buttons in the door as well as the rear seat remote, a 5.7 inch OLED display housed in the beautifully trimmed fold-down centre armrest (which also has a soft close function!). The remote also allows adjustment of the lighting and climate control. Classy.

There’s a shallow storage box and twin cupholders in the armrest, medium size door bins and hard shell pockets on the front seat backs. The rear armrests also feature a small lidded cubby. 

In terms of connectivity and power options there’s wireless Android Auto and Apple CarPlay, a USB-A and USB-C in the front, and an identical pair in the rear, as well as a 12-volt socket in the front and two in the back.

Boot volume is a useful 505 litres (VDA) and the lid is electric, with gesture control. It’s able to easily swallow our three-piece luggage set or the bulky CarsGuide pram. And while the rear seats don’t fold there’s a ski port door to accommodate long items. Just make sure you use the tie-down anchors in the boot to ensure they’re properly secured. There’s a handy netted section behind the left wheel well and a cargo net is included.

Maximum towing capacity, for a braked trailer, is 2.3 tonnes (750kg unbraked) and in more good news, the spare is a space-saver rather than the increasingly prevalent inflator/repair kit.

If you’re buying a Mercedes-Benz S-Class there’s a good chance you’re more interested in the back seat than the front: you could be buying it for a business, or you could like to be driven around - and there are definitely worse places you could be.

We would suggest, though, that the best place you could be if that’s your caper is in the back of a long-wheelbase S-Class model, which has extra legroom. 

And if you happen to be in a LWB model with the 'Business Class Package', you’ll enjoy two individual rear seats rather than a three-seat bench, folding tables for your bento box or laptop, and an ‘executive seat’ on the passenger side that features a foot rest and allows you to slide the front seat forward to liberate more room. Deluxe. 

No matter if you are in one of the stretched models demarcated as such by the ‘L’ suffix or not, you will enjoy excellent seat comfort and good head- and shoulder-room. Legroom in the regular models isn’t as plentiful as you might expect: much more affordable cars like the Hyundai Sonata give the S-Class a run for its money in that regard.

There are good storage options for odds and ends, with the back seat featuring a fold-down armrest with pop-out cupholders and a storage box, as well as map pockets - and the boot space varies depending on the model, but the S 350 d has a 510-litre cargo capacity (VDA). All four doors have bottle holsters, and a bit of extra room besides. Of course there are rear-seat air-vents, and if you’re kids are lucky enough to ride around in a S-Class, the two ISOFIX/three top-tether points will be welcome.

Up front there are two cupholders between the seats, and a new wireless phone charger in the centre console (Qi compatible phones only). There are two USB ports as standard in most models, while models with the rear seat entertainment package fitted get rear USBs. 

The huge screen that runs across two-thirds of the dashboard has seen the noticeable join marker removed for this update, with the monitors being upgraded to a higher resolution and the graphics have been reworked, too. The codpiece-style controller of the Comand media interface remains, and while it still isn’t as simple as other controllers, it is reasonably easy to get used to. 

So … what about Beyonce? 

She comes in as part of the Energizing Comfort Control system, which is standard in some models and a $1400 option in those that don’t have it fitted. 

Essentially it allows you to choose between different set moods: 'Joy', 'Freshness', 'Vitality', 'Warmth', 'Comfort' and 'Training', the latter of which offers three different stretching/exercise programs that last for 10 minutes to stop fatigue. The instructions are given by voice over the sound system.

Each of the moods will adjust the temperature and ventilation (the Freshness setting offers ‘gusts’ of fresh air as if you’re at the beach!), ambient lighting, air fragrance and intensity, and the massage function for the seats. And the music bit - there are predefined songs the system can cue up to suit the mood, or it can identify songs on a hard-drive or USB that suit the programs by analysing the tempo of the tune. Amazing, right?

The new steering wheel looks a lot sportier than the one in the pre-update car, and it has finally done away with the awkward cruise control stalk in favour of steering wheel buttons for the adaptive cruise control system.

If you can call a car that starts near two-hundred grand good value, then you have much more money than I do. But there is no escaping it: the new S-Class 2018 range is better value than before.

The starting point in the range is entry-grade S 350 d, which is $195,900 plus on-road costs. 

Standard kit for that model includes 19-inch alloy wheels, leather trim, heated and cooled front seats, nappa leather-wrapped steering wheel, those great new headlights and the new ambient lighting system, a panoramic sunroof, head-up display, dark brown 'Eucalyptus' trim, auto-dimming rear-view and side mirrors, a wireless phone charging system, keyless entry and push-button start. The entire S-Class range now gets auto-closing doors and an electric boot lid, too.

The media system in the S 350 d includes sat nav with traffic monitoring, a 13-speaker Burmester sound system, digital TV, DAB+ digital radio, Apple CarPlay and Android Auto, and the 'Comand Online' system with internet capability.

Next up the model range is the S 400d L (at $222,500), and the S 450 L ($227,500) - both of which are specified identically. Over the base model car they feature the extended wheelbase, as well as electronically adjustable rear seats with memory function, side window blinds, a rear blind, rear climate control, and 20-inch wheels. 

The S 560 sees the price head north to $270,000 (for the short-wheelbase model, which loses the abovementioned stuff in the L models), or $295,000 for the S 560 L. It adds the following nice features: nappa leather, brown burr walnut trim, a wood/leather steering wheel, 'Energizing Comfort Control', different (five-spoke design) 20-inch wheels, laminated glass and an anti-theft protection package. The S 560 L has luxury rear head restraints - they’re more like pillows, honestly - an individual rear-seat entertainment system and two wireless headsets.

The top of the regular S-Class model range is the Mercedes-AMG S 63 L, which is a princely $375,000. It builds on the kit offered in the models below, and pushes the sports luxury aspect further, with a full AMG body kit, 20-inch AMG wheels, AMG specific drive programs, AMG brakes, an uprated exhaust, sports steering and retuned suspension. Inside there are model-specific elements, special wood trim, front seats with active bolstering, and heated and ventilated rear seats.  

If you’re shopping at this end of the market, then you’ll likely also be tossing up between a BMW 7 Series, or maybe a Bentley Flying Spur. An all-new Lexus LS will arrive in April 2018, and the all-new Audi A8 isn’t far away, either.

The Audi A8 50TDI is powered by a 3.0-litre turbo-diesel V6 engine sending 210kW (from 3500-4000rpm) and 600Nm (from 1750-3250rpm) to all four wheels via an eight-speed automatic transmission (with ‘Tiptronic’ sequential manual shift function) and Audi’s quattro constant all-wheel drive system using a self-locking centre differential.

It also features a 48-volt electrical set-up for mild hybrid functionality built around a belt connected starter/generator, AC to DC converter and a 48-volt lithium-ion battery. 

With energy recovery of up to 12kW from regenerative braking, it enables the A8 to regularly coast with the engine switched off and helps the extended stop-start system to operate smoothly. 

The big news for the majority of S-Class buyers is the new engine in the S 350d, which is a 2.9-litre in-line six-cylinder turbo-diesel with 210kW of power and 600Nm of torque. It has a nine-speed automatic and is rear-wheel drive (RWD).

That same diesel engine is wicked up in the S 400d L, with that model churning out 250kW and 700Nm, and remains rear-drive with a nine-speed auto.

The petrol model range is opened by the S 450 L with a 3.0-litre six-cylinder twin-turbo mill producing 270kW/520Nm. Again, nine-speed auto, RWD.

The S 560 and S 560L run the same 4.0-litre twin-turbo V8 petrol with 345kW of power and 700Nm of torque. Nine-speed auto, rear-drive - naturally!

The AMG-fettled S 63 has a thumping twin-turbo 4.0-litre V8 petrol engine with 450kW and 900Nm, with a nine-speed MCT multi-clutch auto and - you guessed it - RWD.

Audi’s official fuel economy number for the combined (ADR 81/02 - urban, extra-urban) cycle is 6.6L/100km, the 3.0-litre turbo-diesel V6 emitting 175g/km of CO2 in the process.

Over a week of city, suburban, and some freeway running we averaged 11.1L/100km, which is acceptable for a 2.1-tonne luxury sedan.

Also worth noting the standard stop-start system works beautifully thanks to the 48-volt starter/generator.

You’ll need 82 litres of diesel to fill the tank and using the official number, that translates to a range of just over 1240km, which drops to around 740km using our real-world figure.

The diesel models are - unsurprisingly - the most frugal in the range, with the entry-level S 350 d using a claimed 5.4 litres per 100km across a range of disciplines.

The S 400 d L - which uses a higher-output version of the same diesel drivetrain as the model above - uses only a minuscule amount more: its claim is 5.5L/100km. 

The most frugal of the petrols is the S 450 L, with its six-pot petrol twin-turbo using a claimed 8.4L/100km.

Every model has stop-start - including the AMG - and the V8 petrols also feature cylinder deactivation when in 'Eco' mode.

That cylinder deactivation system helps the S 560 achieve an incredibly low claimed consumption of 8.5L/100km. So does the longer, slightly heavier S 560 L.

The higher-out Mercedes-AMG S 63 L uses 9.0L/100km, according to its claim. Amazing for the outputs of the engine.

Despite extensive use of aluminium in the ‘ASF’ platform and body panels, the A8 tips the scales at a sturdy 2095kg, yet Audi says the A8 will accelerate from 0-100km/h in just 5.9 seconds. And with 600Nm of peak torque available across a flat plateau from 1750-3250rpm this big four-door gets up and goes hard when asked to. 

At more sedate speeds you’re occasionally reminded there’s a diesel engine under the bonnet, with that characteristic engine and exhaust noise only making their presence felt under pressure. 

In fact, under normal circumstances, noise, be it the engine, tyres or wind is minimal, thanks to a combination of the car’s aero-efficient shape, thick acoustic glass and other sound-deadening measures throughout the car.

The eight-speed auto transmission is suitably smooth, with the central shifter or wheel-mounted paddles able to make snappy sequential ‘manual’ shifts.

There are four drive modes in the ‘Drive Select’ system - ‘Comfort’, ‘Auto’, ‘Dynamic’ and ‘Individual’ - enabling tweaks to the steering, transmission, throttle and suspension. Comfort felt most appropriate most of the time, although dialling up the throttle and transmission to more aggressive modes in Individual adds an enjoyable edge.

The suspension is five-link front and rear with an adaptive air system smoothing even high-frequency bumps and ruts amazingly well.

Push into a corner and the A8 feels nicely balanced, its wide track, sophisticated suspension, plus the quattro AWD system seamlessly distributing drive between the front and rear axles, keeping the big body under control. In fact, you feel the ‘big car shrinking around you’ syndrome from the get-go.

The steering is precise without being overly sharp and road feel is good. Again, with that 2.1-tonne kerb weight in mind, braking is appropriately powerful with big ventilated discs front (350mm) and rear (330mm).

It pays to remember the turning circle is 12.5m, and it’s worth picking your spot for a U- or three-point turn.

Although there’s a lot going on for the driver in terms of screens, buttons and switches it all makes sense ergonomically. The head-up display is helpful and there’s a common sense mix of digital and physical controls, the latter including an audio volume knob. Yes.

Smooth. It wasn’t even because I’d chosen the Energizing Comfort Control mood to elicit that vibe. It’s smooth - and so it should be.

Whether it’s the near-silent new six-cylinder diesel, which hauls the near two-tonne sedan along with less fuss than a medical centre receptionist dealing with a room full of coughing patients. There is no fuss. You just hand over control to the engine, and trust it will get you where you need to be.

The V8 petrol in the S 560 also has a bit of a silent killer vibe to it. There’s perhaps not as much noise as a V8 fan might want, but the mumbo is there, and in both cars the gearshifts are sublimely timed and super smooth.

Admittedly, the stiff-sided run-flat tyres on both the 19- and 20-inch wheels can exhibit a slight terseness over sharp edges, but when it comes to rolling over pockmarked surfaces or rougher country backroads, the ride offered up by the air suspension with variable dampers is superb. Put it in Sport mode and it stiffens up to the degree you’d expect, but Comfort is no doubt the best place to be.

The steering is super light but accurate, meaning it’s easier than you’d think to pilot this behemoth of a sedan through corners. The grip on offer is excellent, too, even if traction can be an issue - I had a full couple of seconds of strobe light action from the traction control light when I buried the throttle in the S 560. 

I didn’t get a chance to drive the six-cylinder petrol S 450 L, or the S 400 d L. And, I’m really sad to report, there was no opportunity to drive the AMG S 63 L, either. 

But the overall feeling of the updated range is that it remains a deluxe and delightful limousine - whether you have the good fortune of being in the driver’s seat or not.

Easily one of the safest cars, if not the safest car, on the road today if technology is anything to go by. Well, we can’t go by a crash test score, because the S-Class hasn’t been crashed by EuroNCAP or ANCAP. So I can’t really give it a 10/10 for safety…

But when the standard safety kit list is as lengthy as the S-Class’s, it seems a safe bet. Items fitted include a 360-degree camera system, parking sensors front and rear, auto emergency braking, active blind-spot monitoring, active lane-keeping assist, adaptive cruise control with active steering assist, drowsiness detection, crosswind assist, and pedestrian detection with evasive steering assist (which allows you to turn the wheel harder to avoid impact with a pedestrian).

Plus there are other items like the company’s Pre-Safe crash detection system which can flash the car’s hazard lights at other road users, and tighten the occupant’s seatbelt in anticipation of being hit. And if that happens, there are eight airbags (dual front, front side, rear side, curtain).

The A8 is covered by Audi Australia’s five-year/unlimited km warranty, which is now par for the luxury market course, and 24-hour roadside assistance is included for the duration.

Paint defects are also covered for five years, with rust (to the point of perforation) covered for 12. Nice.

Service is required every 12 months or 15,000km with a five-year capped-price plan for the A8 coming in at $3830, or $766 per year. That’s a fair wedge but not outrageous for the category.

Mercedes-Benz offers a standard three-year/unlimited kilometre warranty.

Servicing is due every 12 months or 25,000km on all engines except AMG drivetrains, which require servicing every year or 20,000km. 

Mercedes-Benz has a (pricey!) capped-price servicing plan. The standard diesel and petrol models in the S-Class range cost $596 for the first service, and $1192 for the second and third visits. The costs for the sole AMG model is $736 for the first service, then the second and third visits are $1472 per.