Audi S6 \u0026 S7 (C7) | PH Used Buying Guide

Audi S6 \u0026 S7 (C7) | PH Used Buying Guide

09/04/2022

Audi's mid-tier option wasn't particularly heralded when new. How about now?

By Tony Middlehurst / Sunday, 4 September 2022 / Loading comments

Key considerations

  • Available from £17,000
  • 4.0-litre V8 petrol twin-turbo, all-wheel drive
  • Saloon, estate or 5-door coupe cover all bases
  • Storming speed and grip, steering a bit odd
  • Good reliability, excellent build, lovely cabin
  • Check that the key mech upgrades have been done

Have you ever been to the theatre, been disappointed when they’ve announced that the star turn has had to cry off, and then been pleasantly surprised by the performance of the understudy? 

You could apply that ‘surprise and delight’ principle to the sporting versions of Audi’s family-friendly A3, A4 and A6. RS has of course become the halo sub-brand, but for many buyers, the one-rung-below S models garnered a special appeal of their own. For most, the performance was more than adequate and there were some handy savings to be made on purchase, insurance and parts costs when you knocked the R off the badge. 

Today we’re going to be looking at the big daddy S6 (saloon and Avant estate) and S7 Sportback (five-door coupe) versions of the Type 4G C7 that was launched in 2012, then facelifted and Euro 6’ed for the 2015 model year, and finally discontinued in 2018. 

The S6 name has actually been around since 1996 when the 4.2 V8 S6 Plus version of the C4 A6 first went on sale in Europe in both saloon and estate formats. Available only with a 6-speed manual gearbox, the 322hp S6 Plus was a very low-volume model with just over 850 estates and fewer than a hundred four-doors built in its one-year run. As such it has long been an Audi collector’s piece. There were none on sale in the UK at the time of writing, but to give you an indication of what you’d likely be paying if there were any, an S6 Plus saloon of unspecified mileage was sold by RM Sothebys in 2020 for 50,000 euros.

The S6 version of the 1999-on C5 A6 continued with the Plus’s 4.2 V8, powered up to 335hp. The RS6 model established its place at the top of the A6 sports hierarchy three years later with its bi-turbo’d 444hp V8, but the big change came in 2006 when the Type 4F C6 S6 arrived with a normally aspirated 430hp 5.2 V10 motor. Again there was an RS hiatus, this time of two years, before the range-topper bombed in with its 572hp biturbo 5.0 V10. 

You’ll find a few 5.2 V10 C6 S6s in the classifieds with prices for high-mile saloons starting rather temptingly from under £8,000. For £12k you could get this good-looking Avant but as noted a moment ago we’re focusing here on the 2012-2018 C7 S6s and the new-for-July 2012 five-door coupe version, the S7 Sportback. 

If you want a V8-powered S6, the C7 is your last chance because the current C8 S6 and S7 that succeeded it in 2018 have 2.9-litre V6 engines. Powered by a twin-turbo 414hp 4.0 V8 TFSI unit linked up to a 7-speed S tronic gearbox and Audi’s excellent quattro all-wheel drive system, the C7 S cars were again deliberately ‘overshadowed’ in the range by the 552hp RS model, but in isolation the S6 wasn’t overshadowed by much else on the road thanks to the superb drivetrain and chassis tech that gave it a mid-four second 0-62mph time. 

As mentioned earlier, there was a 7.5 S6/7 facelift in 2015 with a new front-end look (bumpers and lights). These ’15-on cars put out 444hp with no change to either the 406lb ft torque maximum or the key performance figures like the 0-62mph time which remained at 4.6sec for the saloon and 4.7 for the estate and coupe. 

Pre-facelift C7 Avants with around 80,000 miles on the clock are around £20,000, with equivalent saloons being up to a couple of grand cheaper and dipping to as little as £17,000 for 100,000-milers. Used S7 coupes generally have slightly lower mileages than the saloons and estates. They were more expensive than the other two new, and are also perceived to be a bit cooler. Their prices reflect that now, starting nearer to £23k. 

SPECIFICATION | AUDI S6/S7 (C7/4G model, 2012-18)

Engine: 3,993cc V8 32v twin-turbocharged
Transmission: 7-speed automatic, all-wheel drive
Power (hp): [email protected],400rpm
Torque (lb ft): [email protected],400-5,200rpm
0-62mph (secs): 4.7 (Avant & S7), 4.6 (saloon)
Top speed (mph): 155 (limited)
Weight (kg): 2,025 (1,970 saloon, 2,020 S7)
MPG (official combined): 29.1 (29.4 saloon and S7)
CO2 (g/km): 226 (NEDC) (225 for saloon and S7) 
Wheels (in): 8.5 x 19
Tyres: 225/40
On sale: 2012 – 2018
Price new: £54,000 (saloon), £56,000 (Avant), £62,000 (S7)
Price now: from £17,000 (saloon), £20,000 (Avant), £23,000 (S7)

Note for reference: kerbweight and power data are hard to pin down with absolute certainty. For consistency, we use the same source for all our guides. We hope the data we use is right more often than it’s wrong. Our advice is to treat it as relative rather than definitive.  

ENGINE & GEARBOX

The 4.0-litre twin-turbo ‘hot vee’ V8 that was used in the new Bentley Continental GT and by Audi in its own S8 was also used in the S6 and S7, albeit detuned to 414hp from the S8’s 513hp. Stage 1 tuning would take the output back to S8 levels and 600hp-plus is achievable when you go to stage 3. 

The 4.0 V8 was a honey-smooth piece of kit in any iteration. It wasn’t a massive revver, the redline being set at 6,500rpm, but high gearing made it a formidable nation-vaulter and heavy low-rpm torque gave it impressive squirt off the line. 

It wasn’t perfect though. There were clogging issues with turbocharger oil screens which could lead to oil starvation and catastrophic turbo failure on 2013-2017 cars, typically when the mileage was in the 35-50,000 range. That could cost over £5,000 to put right. This was all a bit ironic as the point of the screens was to protect the turbos. A revised ‘G’ screen that was more resistant to clogging was put out by Audi but we’re not sure if that was ever part of an official recall. The location of the screens meant that the turbo units had to be removed in order to access them. Even with an unclogged screen, turbo compressor wheels have been known to crack and fail, especially on mapped vehicles. We believe that these compressor wheels were cast on the S6 and S7, whereas on cars like the RS7 they were billet. 

PCV oil separator failure was another known issue on these cars, signified by a loud and quite annoying whistling noise. If you pursued it hard enough this would be fixed gratis by Audi under extended warranty, depending on mileage and age of course. The part itself wasn’t that expensive but fitting it was a labour-intensive job. If your S6 or S7 got the whistle and you’d been planning on upgrading your engine hardware anyway that would be the time to do it. If the engine was struggling to start itself that would very likely be down to a malfunctioning high-pressure fuel pump. Budget £1,200 to fix that. 

If you put the Drive Select into Dynamic the flapped exhaust plus sound actuator would do its best to amplify the V8’s noise ANC (Active Noise Control) blotted out any less pleasing sounds that might escape when the engine was running in half-shutdown V4 mode to minimise fuel consumption. Talking of which, real-world figures could easily drop below 15mpg, but 30mpg was entirely doable on a motorway cruise and another PHer reported 43mpg on the Swindon-Heathrow run. Somewhat better than the numbers you might get from a V10.

Instead of the beefy 8-speed ZF 8HP90 torque converter gearbox that went into the S8 and the RS6, the sporty A6 derivatives ran with the DL501 7-cog twin-clutch S tronic unit. This worked well apart from a degree of clonking on lower-speed downshifts. It was wise to bear in mind the DSG box’s lighter-duty nature when considering your tuning options, but anecdotally there’s not that much evidence of DL501 transmissions blowing under stage 1-type remap pressure. Back at the end of 2021 one PHer had a lovely Sepang Blue pearl ’16 S6 that he told us had been custom remapped to a safe (at the time of posting anyway) 563hp/550lb ft. Having said all that, a small number of Mechatronic units conked out, making it difficult to engage a gear. Sorting that might entail the fitment of a new transmission at around £5k. 

On servicing, either the MMI or myAudi account will tell you when a service is due. At a fairly well-known UK independent, you’ll pay around £230 for an oil change (10,000 miles, or 5,000 on tuned cars), £300 for an inspection service which includes and oil change and pollen filter, and £600 for that plus an air filter and spark plugs. A gearbox oil change every 38,000 miles will be about £400. Brake fluid services are every two years and £80. A complete diff oil change (front, centre, Sport and rear)  will be £500. Sounds a lot, but centre diff fluid is £115 a litre at the moment. 

You’ll naturally pay a lot more if you go to an Audi dealer. Audi UK is currently offering 0% finance on servicing and repairs and there’s an independents price-matching scheme but you have to jump through a lot of hoops to make it stick. 

CHASSIS

No C7 S6 or S7 came in at much under two tonnes, so it was unreasonable to expect Elise-like handling delicacy. All the same, Audi did a pretty good job of tying these beasts down to the ground. 

By default, Audi’s all-wheel-drive system delivered 60 per cent of available torque to the rear wheels, rising to 80 when appropriate. All three cars had adaptive air suspension as standard (without the steel optbackability that the RS models had), along with a Sport rear differential which would throw more torque at an individual wheel that was capable of taking it, as opposed to the commoner method of applying braking force to a wheel struggling for grip. The positive effects of that Sport diff could be most clearly felt in poor weather conditions.

Of the three choices on your Drive Select knob, Comfort, Dynamic and the compromise Auto mode, ride quality in any of them was perfectly acceptable and less firm than the RS5’s, but the steering was artificially heavy in Dynamic mode and kind of overdid its attempts to speed up any changes from straight ahead, resulting in an artificially ‘jinky’ drive. At the other end, Comfort steering was light but very detached. It’s worth getting the steering as good as it can be by making sure that all the software updates have been carried out. 

The reliability tale on the chassis side is very good but there have been incidences of sticking electronic handbrakes. Creaking wishbones have been a thing too. The popular fix for that was to throw them away and replace them with RS5 items. 

Active engine mounts could prematurely fail. One theory for this was the running imbalance caused by the cylinder deactivation system. These were expensive to fix. Carbon ceramic brakes were on the options list. The normal steel brakes were closer in spec to the regular A6’s than the RS’s and therefore a fair bit cheaper to replace. 

As with any car offering air suspension, the systems used by Audi were not immune from problems. Shocks are prone to leaking on higher mileage cars and they tend to need replacing in pairs. It’s tempting to go with aftermarket replacements to keep the costs down but even independent specialists will often counsel you to stick with OEM items. 

BODYWORK

The S6 and S7 might not have had the intimidatory road presence of the RS but not everybody wanted that look in a car. The S style was more subtle, but relative to most of its rivals it was still a powerful look thanks to the chromed quad exhausts set off by a diffuser, the stylish alloy wheels and the profusion of aluminium trim touches. The paint palette was sober too, to the point of tedium in the eyes of some, but dark colours were ideal for slipping under the radar. As one PHer has put it, put a Xerox sticker in the back of an S6 Avant and it wouldn’t raise suspicion in a Mitchells & Butlers lunchtime car park. There are some brighter colours about, though not many of those are for sale. 

Despite the decline of the saloon generally, the four-door body format hasn’t disappeared from the S6 range and it’s a decent foil to the Avant estate which as we all know is a handsome and practical beast capable of carrying up to 1,680 litres of cargo. The saloon does well too though with a very creditable 995-litre boot when the back seats are down.

If you see a tiny lens in the centre of the grille of a car you’re looking at (just below the four Audi rings) that means it has a front camera, which in combination with similar lenses in the door mirrors will give you cool top-down and ‘surround’ views of the car. Another camera lens inside one of those rings means you’ve got night vision. The release on the fuel filler cap could break, a potentially major inconvenience if it happened at the wrong time. The fix usually involved the fitment of a new actuator.

INTERIOR 

The C7 cabin is a special place in which to ensconce yourself and possibly even congratulate yourself on the wisdom of your purchase. In S6/7 owner surveys, interior design generally came out on top of the pile. As you’d expect from a high-range Audi you got a strong spec with Valcona leather throughout, supportive S6/7-exclusive multi-way powered and heated sports seats, a stitched S quattro steering wheel and some convincing aluminium-look shift paddles. 

The tech was well presented and not too overpowering. Some owners reported non-emergence of the infotainment screen from the dashtop. All C7s had round steering wheels, some of which would be heated (along with the back seats) if your car had the cold weather package, whereas any C7.5 facelift with a flat-bottomed wheel will not have heat in the wheel or the rear seats. Although the S7 had five doors, it only had four seats. It was Audi’s answer to the Mercedes CLS.

PH VERDICT

We’ve listed a few common faults here because this is a buyers’ guide and it would be remiss of us not to, but don’t let these have too much of a negative effect on your view of the S6 and S7. The vast majority of S6/S7 owners love the speed, acceleration, surprising economy in mild use, space, luxury and near-unimpeachable build quality of their vehicles and have enjoyed great reliability over often high mileages.  

The downside is a certain ‘coldness’ in the drive. If you place more value on that side of things you might prefer something like a Jaguar XFR, although of course that wouldn’t give you the option of the S7’s useful five-door bodystyle. Otherwise, you might consider the main rival to one of these to be a C7 drinking from the other pump, like a biturbo Allroad, or even an earlier C6 V6T. They’re all fine cars and they’ll all give you a strong sense of pride in ownership. 

One good thing that seems to be happening in the used C7 market is a compression of the price gap between early 2012-15 414hp cars and the 2015-on 444hp facelifts. This compression wasn’t quite as obvious in S6 saloons up for sale on PH Classifieds at the time of going to press, when there was a £7,500 gap between the cheapest on offer – this 74,000-mile car at £17,490 and this 444hp facelift at just under £25k – but PH doesn’t have all the C7s on sale, and that £25k car was a Black Edition. 

Outside of PH we found an S6 facelift with upgraded turbo oil filters in place for £18,750, the message there being that if you’re on a tight budget don’t just meekly assume that you won’t be able to afford one of the later cars. On the other hand, don’t dismiss pre-facelifts either as there’s really little if any difference in terms of the on-road performance. And don’t necessarily dismiss the saloon on space grounds either because the boot is big. 

PH’s lowest-priced Avant at the time of writing was this 2014 car in black with 64,000 miles at £24,995. For a facelift Avant off PH you’ll be starting at £28,547 for this 2018 81,000-miler in dark blue. The most affordable S7 was this 2013 78,000-miler in ice silver with black leather and fine grain ash wood at £23,444 but for only £1,500 more you could be into this one-owner 63,000-mile facelift car with the 444hp engine. 


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