Free guide · 2006–2011 · 5.2 V10 FSI
Audi S6 C6: what to check before you buy
What this car is, and the six questions that decide whether the one you are looking at is a good buy.
In this guide · 6 chapters
Who built it, and what they built
The C6 A6 was drawn by Satoshi Wada around 2001 and went on sale in 2004, under Walter de Silva as head of design for the Audi brand. It wears the single-frame grille, which Audi had first put on a production car with the W12 A8 and which then spread across the range. Look at one now and it is unremarkable, which is the point: it was a business saloon, sold to people who wanted a business saloon.
Then Audi put ten cylinders in it.
The engine, and the story you will be told about it
The S6 has a 5,204 cc V10 with direct injection, naturally aspirated, 435 PS at 6,800 rpm and 540 Nm between 3,000 and 4,000 rpm. Ten spark plugs, ten coils, ten injectors.
You will read that it is the Lamborghini Gallardo's engine. Be careful with that, because the sources do not agree and this guide would rather be right than exciting. Wikipedia records that the engine is "often referred to as a derivative of Lamborghini's 5.0-litre V10" and that it is based on Audi's own 4.2 V8. Autocar's buying guide for this exact car quotes a specialist, Martin Adams of Unit 20, who says the S6's V10 "is erroneously linked to the dry-sump V10s in the RS6 and Lamborghini Gallardo, but it shares little with them."
So here is the sentence that is actually defensible, and it loses nothing: ten cylinders, no turbocharger, in a car with rear doors and a boot. Nobody sells that now.
One transmission, and no manual
The ZF 6HP26 six-speed tiptronic, with quattro. There was one transmission and it is an automatic, so an advert offering a manual is describing something else.
And the thing that decides what one costs to own
The four timing chains sit at the back of the engine. Not the front. That single fact is why a chain job on this car is as big as a job gets, and why this guide gives it a chapter of its own. It is not that the chains fail often. It is that the price comes from where they are, and there is nothing anybody can do about where they are.
How the figures in this guide work
How much work each job is, not what it costs. Every point in this guide carries an effort — an hour or two, half a day, a day, two or three days, or a week or more in the workshop — plus a line saying whether the money sits in the part or in getting to it.
There are no prices, and that is deliberate. What a job costs depends on which country you are in and which workshop you walk into, so a figure I cannot verify is worse than no figure. If you want money, ask any workshop one question — what is your hourly rate? — and every hour in this guide becomes your own number, in your own currency. One question, and the answer is actually true for you.
None of this is advice about one particular car, because I have not seen the car you are looking at. Have every one of them inspected before you buy, by someone who knows this engine.
The six questions that decide whether this car is a good buy
These cars are between fifteen and twenty years old, and the difference between a good buy and an expensive one has very little to do with the asking price. It comes down to six questions, and on this car most of them are answered by paperwork, a diagnostic read-out and a cold start rather than by driving it.
1 · The timing chains, and specifically the tensioners.
The chains themselves are reliable; what can fail is what holds them — the plastic guides and the tensioners. Untreated it can end the engine. It gives itself away in one moment only, on a cold start, which means you get one chance at it per viewing, and it means the engine must be genuinely cold when you arrive. Everything about how you arrange the appointment follows from this one sentence.
2 · The camshaft adjusters.
They carry the camshaft sprockets, so they sit in the chain drive at the back of the engine — the same end as the chains, and the same access. A fault can be an adjustment valve or the adjusters themselves: a small job or a large one, and only an investigation tells you which.
3 · How much oil it uses — and what the owner thinks is normal.
This engine drinks oil, and owner reports of regular topping up are common enough that you should treat it as characteristic rather than as a fault. The question that matters is not whether it uses oil. It is how much, whether the owner has a number, and whether it is getting worse — and whether the oil going in is the right specification at the right interval, because on this engine the chain tensioners work on that oil.
4 · The ten ignition coils, and why the test drive is not enough.
Ten coils, and a test drive will not tell you which of them is failing. There is a read-out that does, and it is the difference between replacing the coils that need it and a long search.
5 · Which suspension it actually has.
Audi built the S6 on steel springs with its own, firmer tuning, and that is what you should expect to find. Establish what is under the car in front of you before you price anything that touches the suspension.
6 · What has already been paid for.
On this car the odometer tells you less than the folder does. Carbon cleaning, ten coils, chain tensioners, the right oil at the right interval: none of it shows in the mileage and all of it shows in the invoices.
What the honest answer to all six looks like
On a car with history, where the known items have demonstrably been done, an owner gets through a fraction of the list in the first two years, and none of the heavy jobs — not because things break, but because things arrive that were always going to arrive. On this car the point is not the size of the bill; it is that almost nothing on a V10 is reachable, so what you are buying is somebody's time.
The buying guide takes each of these six apart, adds the things that are simply fifteen years old, and gives every one of them how much work it is, what tells you about it at a viewing, and whether it has to be done now or can wait years. It ends with a card you print and take with you, in the order you do it, including the one moment at a viewing that comes only once.
Which years, which specification
The S6 C6 was built from 2006 to 2011 with one engine and one transmission: the 5.2 V10 FSI, 435 PS, and the ZF 6HP26 six-speed tiptronic, driving all four wheels.
There was one transmission, and it is an automatic. That is your fastest filter on an advert.
And do not confuse it with the RS6. The C6 RS6, from 2008, has a twin-turbocharged 5.0 V10 with 580 PS. Different car, different engine, different money, and a completely different maintenance picture. If a seller uses the words S6 and RS6 in the same advert, establish which one you are looking at before anything else.
Saloon and Avant. Both were sold, both drive much the same, and the Avant carries a dog.
The facelift, in 2008, brought revised lights and detailing. For what you are going to check it changes very little. The main rule stands: buy the best-maintained car, not the newest one.
What you must establish per car:
The suspension. Audi built the S6 on steel springs with its own, firmer tuning. Ask whether anything has been changed, and then verify — the seller is often not sure. This decides which suspension points in the buying guide apply to the car in front of you.
The equipment. These were expensive cars specified by people who ticked boxes, so two cars from the same month can differ a lot. None of it is rare enough to hunt for, and none of it is worth paying a premium over condition.
Check that it is a real S6, which is straightforward: a V10 badge on the front wing, an S6 badge in the grille and on the boot, and — the part that actually settles it — ten cylinders when you open the bonnet. A well-made A6 with S6 parts is not unheard of, and on a car at this price checking is not suspicion, it is a standard check.
Beyond that, look for a car nobody has modified. Factory wheels, standard ride height, the original exhaust. A remap on a naturally aspirated V10 buys very little and tells you something about the previous owner.
What it is worth
This is the hardest thing to establish on your own and it does more than anything else to decide whether you buy well. I am not going to give you a price list — it varies by country and by month, and an out-of-date number is worse than no number. I am going to give you the method.
Compare on paperwork, not on mileage. On this car more than on most, because the two things that decide what it costs you — the chain tensioners and the oil regime — leave no trace anywhere except on paper.
There are three kinds of car for sale, and each one deserves a different offer.
The documented car. Full history, invoices tied to readings, and an owner who knows when what was done. Asking price at the top of the market, usually justified. What you are buying is the history rather than the car.
The tidy car with no paperwork. Drives well, looks well, and the owner says everything has been done. The hardest of the three, because there is nothing to see. You buy it on the condition it is in today and you budget the top end of everything in this guide.
The project. Known work, price adjusted to match. On this car, be careful with this one in a way you would not be with a cheaper model: a project S6 with a question mark over its chain tensioners is not a project, it is an engine.
How to set the three against each other. Take the asking price, work through both lists, and add up what is coming in the first two years. Call that the entry price. Then compare entry prices rather than asking prices, and the most expensive car turns out surprisingly often to be the cheapest.
Where to look: your country's big classified sites, the Audi specialists, and the auction sites. Follow the market for a month before you go and see anything. You do not need to know what one is worth; you need to know what is happening — which cars sell quickly, which sit for months, and at what price.
And one thing specific to this model. These are cheap to buy and they are not cheap to keep, and the market knows it. A car priced well below the others is usually priced there for a reason that is written down somewhere. Find the reason before you find the money.
What it is actually like to own one
Ten cylinders idling is a sound you do not get from anything else on the road, and it is the first thing owners mention. Not loud — this car is not loud — but layered, and completely unlike a six or an eight. Then you use it and there is no step, no surge, no waiting: 435 PS arriving in a straight line to 6,800 rpm, with quattro underneath it putting all of it down in the wet without drama.
It is not a light car and it does not pretend to be one. What it does is cover ground. Long distances at speed, in near silence, with four people and their luggage, and then a downshift that reminds you what is under the bonnet. That combination is the whole reason to own one.
Then it goes back to being an A6. Nobody looks at it. The badge on the wing says V10 and almost nobody reads it. Of everything this car does, that is the part owners talk about most — that it does not announce itself at all.
What it costs you in attention. More than a modern car, and be honest with yourself about the oil. This engine uses it, you will be checking it, and the chain tensioners work on that same oil. That is not a chore you can skip on this model; it is the maintenance.
And it drinks fuel. Ten naturally aspirated cylinders, and you are going to use them.
What it gives back. It has stopped depreciating the way a modern car does, it makes a noise nobody can place, and there will be fewer of them in ten years than there are now. That is not an investment and you should not call it one. It is ten cylinders in a car that looks like a company lease, and that joke does not wear out.
The buying guide — €24
Everything above is what the car is. This is what you check.
Seven faults that belong to this engine, taken apart one by one, with how much work each repair is and how to tell which of them you are looking at. Eleven things that are simply fifteen years old, every one with how much work it is, what tells you about it at a viewing, and whether it has to be done now, within a year or two, or not at all. The five places water and corrosion get in, and the one of them that costs real money. The four timing chains at the back of the engine, why that one word decides the price, and the first seconds of a cold start that give them away. The viewing in eleven steps, including the cold-start moments that come only once. The sentences you say to the seller, and how to build an offer out of what you found.
And a card you print and take with you — fifty-two lines, in the order you do them. That comes as a separate file, because nobody wants to print a whole guide to take a few pages to a car park.
This is what one of the eleven looks like
6 · Discs and pads
Half a day · expensive part, easy access These are S6 sizes and there is less choice than on a normal A6. Good alternatives to the factory discs exist, but cheap it will not be. How you notice it: a lip around the edge of the disc, scoring, and thickness measured on the lift rather than guessed through the wheel.
Expect it within a year or two even if it just about passes now.
And this is how the card reads
- 1 · The cold start · stand at the gearbox end, and do nothing else
- 2 · Ten cylinders, cold
- 3 · The boot · before anything cosmetic
- 4 · Round the outside
- 5 · Inside, ignition on
- 6 · The test drive · two things it must include
What €24 buys, put next to what it saves
A chain job on this engine is a week or more in the workshop, and the parts are a small fraction of it. The guide is €24. It will not stop any of that from being needed — but it does tell you which of them you are looking at before you agree a price, and that is the whole of the difference between paying for a car and paying for someone else's postponed maintenance.
Why there are no prices in it
Because a price we cannot verify is worse than no price, and because a price would be wrong for most of the people reading this anyway. Workshop rates across Europe differ widely, and so do parts prices. A quote from a specialist in one country tells you nothing in another.
What does not change is how much work a job is — that follows from what has to come off the car. So every point in the guide says whether it is an hour or two, half a day, a day, two or three days, or a week or more in the workshop, with a labour figure where a source gives one. And it says whether the money sits in the part or in getting to it, which is what lets you tell a fair quote from a bad one.
If you want a figure, ask any workshop one question — what is your hourly rate? — and every effort level in the guide becomes your own number, in your own currency. One question, and the answer is actually true for you.
How this guide was put together
Because you should know before you pay for it.
- Every fault and symptom comes from a source the guide names, the manufacturer's own documents first. The effort levels are our assessment, unless a source gives the hours.
- Where the sources genuinely disagree — and on whether this V10 is the Gallardo engine they do — you get what each of them says rather than the version that sounds better.
- The effort of every job is counted item by item and checked against the list before every edition.
- It says as plainly what you can leave alone as what you have to do. Four of the eleven age points start from leave it.
Leave your email address at the checkout and both files arrive straight away: one guide and one card, as two pdfs. No subscription, no account.
The full guide · €24
21-page guide, A4 and phone · 4-page inspection card · instant PDF · VAT included
Have every car inspected before you buy by someone who knows this engine. This is general information about the model and not advice about a specific car.