What’s that about slowing down with age? Either the old boys of the Audi arsenal didn’t hear that message, or simply chose to ignore it … we drive the RS7 Performance and the S8 Plus.

For: S8 – great chassis, copes with extra oomph. RS7 – impressive urge and soundtrack, beautifully honed brakes and steering; well-dressed cabin.

Against: S8 – looks and feels dated, pegged back by out-moded tech. RS7 – compact interior, wooden ride.

Scores: S8 – 3/5; RS7 4/5.

ELEVEN years have passed since Audi first decided to liven its A8 limo – just four have clocked by since the same division gave the A7 the same sort of tickle up.

But, of course, the donor models behind the same-engined S8 and the RS7 are older still. Accordingly, the just-launched updates – expressed as a ‘Plus’ descriptive for the big sedan and a ‘Performance’ tag for the large hatch - seems a signal of both facing up to the final countdown. The ‘P’ words both effectively mean one thing: Extra performance.

Is this enough to disguise their wrinkles?

S8

HOW ironic that the hottest A8 I’ve ever experienced should leave me and my wife feeling very, very cold.

Emotionally? Yes, but I’ll get back to that. No, physically. For some strange reason that perplexed us, and the dealership staff who – despite their best efforts – couldn’t find a fix, the test example’s air conditioning went nutsy.

No matter how the knobs were fiddled, or what temperature setting was chosen, whether the air con was on or off … it simply sought to blast out freezing air. Not something that made significant open road runs spread over two days, each of several hours’ duration, at all enjoyable. In all the years … actually, decades … I’ve been testing cars, I’ve never struck this and potentially never will again. Before you ask: Yes, I sought professional assistance. And, yes, the dealer staff in Wellington, though they tried every solution short of pulling apart the dash (not convenient for us, given time limitations), were also perplexed. The diagnostic test said it was okay and, yet they agreed, obviously …

So there was that. Then there was the car itself. Conceivably, there’s a ton to like about the A8 and even more when it arrives in $254,900 S8 guise, simply by virtue of its basic construct and drivetrain layout – even though the Seven Series also comes in four-wheel-drive now, it’s not the same as Quattro. And, frankly, the alloy construct of the A8 is really special, too. And yet, though the luxury and quality is as you’d expect from a big car for the top end of town, it no longer feels, or looks, as leading edge as it once did.

The design doesn’t look outright old, but it does seem dated: What doesn’t potentially help is that, aside from the usual headlight upgrades (now to laser-assist beams that are stunning and offer, I kid you not, 966,105,422 light combinations), the car’s shape has never changed at all: So an example from the start of the current generation could be confused, at a glance, for today’s S8.

The years have taken toll inside, too. As many of the same interior virtues that were once purely associated with the flagship can be found in lesser Audis, often in improved form.

For a reminder of how fast tech changes and how quickly cars with everything can be left behind, look to the infotainment set-up. Though it only underwent a freshen in 2014, some of the in-cabin tech clearly couldn’t be updated.

Most obviously, it misses out on the brilliant Audi Virtual Cockpit display, but everything else about its electronic architecture seems locked into an earlier, now bygone era. There’s infotainment and phone-pairing shock: Bluetooth pairing avails but the setup isn’t that quick and, if you’re into you’re tunes and podcasts, forget about CarPlay and all that latest new-age stuff. This is a new car lacking USB ports and requiring, instead, a special cable (absent from the car) to connect a phone.

The mapping display is also obviously older, and less reactive, than what’s found in latest VW Group fare and, even though more driver assists have been added, you’ll find even more whizzy electronic enables and assists that come in the Seven and Benz’s S-Class, which mightn’t matter if there was a compensating price position. But there isn’t.

Nevertheless, every detail is beautifully engineered. A mixture of traditional wood, supple leather and more modern materials, such as aluminium and chrome highlights, lit by subtle interior lighting, exudes impression of quality and robustness. Plentiful electric adjustment for both the driver's seat and steering wheel is appreciated, while all-round visibility is extremely good.

At over five metres in length, the S8 also lends a lot of metal for your money, but that doesn’t translate to massive spaciousness for a rear-seat passenger. Headroom back there is at a premium, and rear legroom only so-so. Additionally, because the rear seat cushions are set as low as possible to maximize headroom, you feel as if you fall into the rear seats. In terms of boot space, there are only 510 litres of luggage space.

So where’s the ‘why buy’ angle? It’s purely the performance and dynamic ability. If you’re late for a meeting, this is exactly the kind of executive express to hail. Making 445kW and 700Nm (rising, briefly, to 750Nm on overboost), this 4.0-litre twin turbo petrol V8 is a monster.

Zero to 100kmh in just 3.8 seconds is more than a little ludicrous for a luxo-barge, let alone a top speed that’s almost three times our highway limit. But the ‘b’ word doesn’t apply to the S8 – it’s a taut, large-sized sports sedan for which a walloping and quite intoxicating powerplant seems a remarkably natural fit, because of all the finessing undertaken by Audi’s dynamics engineers.

An S8 has a special steering tune and the adaptive air suspension that allows the driver can select from five different modes to influence the car’s ride-height, depending on whether sports or comfort settings are preferred, is also tailored for warp speed acceleration. You’d imagine a lot of this would be wasted away from the autobahn, but in fact it doesn’t work out that way: The car feels really deft, for instance, on winding secondary roads, far more so than its contemporaries. The chassis has brilliant balance, the brakes demonstrate a reliability that suggests this car could probably stand a track day.

Huge pace aside, the engine also has an impressive seamlessness about it; even though when it is sounding quite unruly, it does so in a precisely controlled manner.

So it’s hot. Which takes up back to that troublesome HVAC system: On the very last day of our drive, it suddenly came right – fortuitously, this being a frosty morning. So, one of life’s mysteries resolved.

Even an apparent ability self-remedy, though, cannot save the S8: It’s not the best choice among the best large luxury sedans and even it was, in this SUV-centric market you’d have to think the Q7 simply makes for smarter buying: You’re trading off on stonk but it’s far more modern, much better equipped and likely to hold far stronger residuals.

Of course, if you absolutely must have V8 sizzle, then there is a better way …

RS7 Performance

…. and here it is. RS cars are special brew to start with so the whole concept of anything of this ilk being treated to even more of a stoke-up is … well, unless you’re utterly insane, then the words scintillating’ and ‘scary’ potentially provide good summary of this $224,900 offer.

Another ‘s’ word also slips into mind, too. Calling the RS7 Sportback a supercar doesn’t quite work, because it hasn’t the right look for that special group. Nonetheless, it emphatically has the right kind of shove, both off the line and overall to cause shock and awe amongst the Porsche set and Ferraristi.

Even though it’s only a touch quicker to the legal open road limit than the S8 (or, in fact, the ‘regular’ RS7), with a claimed 3.7s, and only has a dab more power and torque than the flagship – with 445kW and 750Nm (which 33kW and 50Nm more than the standard RS7) it immediately and consistently feels s-o-o-o-o-o-o much more furious and fight-ready. Even at idle, there’s a ferocity about it that suggests stoush-readiness.

There’s just so much urge; the amount of thrust and traction is mind-boggling, wholly and dangerously compelling. Example: You’re stuck behind an 80kmh dawdler. An overtaking opportunity arrives. Plant boot – not heavily, just a tap really – and within scant seconds Mr Slowpoke is but a dot in the mirror and the head-up display is showing a three-figure count that would likely make a headline for all the wrong reasons. It’s that kind of car.

And, like I say, you don’t even need full throttle, or to play with the eight-speed auto, or even have the car in its most extreme performance setting, though that is very much the most aurally satisfying if you enjoy an increasingly raucous basso note accompanied by the occasional raspy, pop-and-crackle.

Again, though, it’s the completeness of the package that does the job. Though, like all RS cars, this one has a wooden-ness to its ride quality no matter how it’s set – doubtless the ultra-low profile 21-inch rubber doesn’t help - it also has ability to corner with a confidence that simply belies its five metre by 1.9m size and, certainly, that 2030kg mass.

To be fair, perhaps it is slightly better at accelerating out of corners than it is at slowing down into them – maybe the ceramic brakes weren’t quite up to operating temp - and, if you push very hard, the all-wheel-drive underpinnings mean you are likely to experience some understeer, and even some very minor torque steer too, but even so the traction and cornering grip from that Pirelli P-Zero footwear is something else.

The car’s potential also exudes in its look: The hatchback silhouette has aged well, but that sleek profile looks all the more hunkered and impressive in the full RS regalia. It’s even more hot-rodded than the S8 and lends itself more naturally to that kind of transformation.

Buy an RS7 and you’re forgoing ability to carry more than two back-seat passengers, because the rear chairs are individual buckets, but that’s hardly a drawback. While the A7 line also isn’t quite as modern as it could be (again, no latest-era infotainment) it is nonetheless considerably more modern in its feature content than the S8 and the design of the cabin in general seems smarter and more in tune with today’s tastes. Again, you get premium trim; those diamond-stitched leather and Alcantara seat treatments are very tasty.

It’s just a better car, potentially a collectible, in fact. Hard to say if the RS7 needed more grunt, because it has always been an especially brutal model, but it certainly doesn’t waste anything of that enhancement. It’s a truly special car.

Verdict

Since the beginning of human history, we have been trying to find ways to stay young. Yet ageing is inevitable, and there seems no way to reverse the process: Each of us is born with an internal biological clock, figuratively speaking, that determines our life span.

Same goes with these cars. The A8 has been an Audi landmark, but it increasingly seems like a car for a past era: Not just because it feels dated, but because large luxury – in this market at least – seems to better present in SUV rather than sedan packaging. As much as anything else, that reflects in the A8's especially sobering residual values. surely nothing in Audi-dom loses value quite as rapidly as one of these.

The RS7 is a much better proposition. Same basic mechanical ingredients but to a much tastier recipe. It’s a pricey car, but a less expensive and more rewarding experience than the S8 offers.