Audi A6 (C6/4F) 2004-2011

On one side there is this spacious, safe, affordable and still not bad looking car with a well-built interior, which can be equipped with a great 4WD system.

But on the other side this exact same car:

• can leave you stranded far away from home
• has some weak points which can lead to a significant engine or electronics damage
• can be equipped with a couple of extremely overpriced spare parts-while the high price is not justified at all

This can sound a bit scary, but with preventative maintenance and with a little bit of luck it’s absolutely not hard to reach 400 000 km / 248 000 mi and more + even avoid most of the issues. And actually, currently there are 52 of these vehicles for sale in Germany which have more than 400 000 km (and 52 is actually not a low number for a German used luxury car with this kind of a mileage).

The Audi A6 C6 was available as a:

Saloon/sedan

Avant/estate

A6 Allroad

Long version – extended wheelbase saloon models with bigger rear seat legroom made exclusively for China

Of course there is also the S6 (S6 review here) and the RS6, but let’s just focus on the regular models.

There is nothing special about the saloon or the Avant models and actually there is nothing really special about the A6 Allroad either (unlike the previous generation Allroad which was a highly modified A6). Since this is just an Avant version which is standardly equipped with a plastic body kit, with the Quattro 4WD system and with the adaptive Air suspension, nothing more nothing less (low range gearbox or stronger body? forget about that). The plastic body kit usually has a default grey look, however it can be also painted in the color of the body – this was a factory option back then.

Interior

The interior of this A6 is spacious, well built and user friendly even at this day and age.

The dashboard is ergonomically inclined to the driver and all the switches are where they should be. However you have to get used to all the buttons on the AC panel and on the MMI system panel. But after getting used to these buttons you can with no problem choose the right category or change the temperature easily even while driving which is something you can’t really do on a touchscreen. + The MMI multimedia system is faster and it has also nicer graphics than the early iDrive in the BMW 5 series E60. It’s also worth mentioning that the facelifted A6 made after 2008 got an updated MMI system which has even better graphics and faster navigation system.

Moving on to the materials quality, everything in the interior is most of the time in a great condition without noticeable wear. However there are some parts which can be worn out more often: specifically the windows control switch, the MMI center button surface or the keyless start stop buttons. Next, the side part of the driver’s side door panel can be cracked + in the oldest cars there are also examples of disintegrating wood trim layer.

When it comes to build quality, yes, it really is on a very high level and it’s definitely better than in the BMW 5 series E60. Almost everything feels really solid starting with the seat side plastic covers thru the dashboard and to the door panels-which are like literally rock solid unless someone disassembled and badly assembled these parts of course. But nothing is perfect, so cars equipped with the stiff factory sport suspension can make rattles from the dashboard on bad quality roads, and the front center armrest can make creaking noises in hot weather.

The standard equipment contains basically nothing spiced with a standard monochromatic multimedia system display from the previous century. The optional equipment on the other hand contains almost everything including soft close doors, double glazed windows, solar sunroof, leather seats with leather dash, ambient lightning package, electrically adjustable and heated steering wheel, parking camera and all that other stuff. But surprisingly there are also things you can’t get in this car, like: ventilated front seats, head up display, night vision, massage seats or heated windscreen. This is interesting since all these things were available in the BMW 5 series E60 except the heated windscreen. On the other side most of the people won’t necessary need these things, although the ventilated front seats are definitely a great feature in the summer…

Fun fact: this is the first A6 which can be equipped with a leather covered dashboard, since this feature was not available in the older A6 C5 and it’s also not available in the successor of this car – the newer C7 model. But the newest C8 models can be again equipped with this feature.

When it comes to music interface, or connectivity, or music user friendliness, whatever you call it, this car is not that hopeless! There is of course the usual CD changer which nobody really uses nowadays, but you can also find cars which are equipped with a “magic box in the glove box” – called the AMI (Audi Music Interface). With this interface you can connect your phone thru the usual AUX cable, or you can connect an USB flash drive and play the music thru these sources. Cars after the facelift got an update in this field – so they can be equipped with the updated version of this AMI in which you can put SD cards (on the picture below).

Lastly, there are 3 types of front seats you could have in these cars:

Possible problems

1. Some electronics

-The usual stuff like the door locks, the window regulators or the keyless entry door handles can of course break, so first thing first check these basic features. (how to remove the front door panel video)

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2. Front door speakers

-Then it’s good to check the main front door speakers which can rattle, so turn up the volume and listen for a speaker rattle. If you hear it then you should know that it’s caused by a plastic speaker dust cap which is glued on the speaker. The glue gets weak over time→the dust cap gets a little loose→and you get a rattle. In this case you can remove the dust cap and re-glue it back, or you can buy a new speaker, whatever you want.

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3. Steering lock

-After this there is the electronic steering lock which can fail and which can leave you stranded since you won’t be able to start the car. The faulty steering lock can be replaced by the dealer, it can be repaired or it can be even deactivated if you find the right person. I did a separate video about this issue so you can find out more here.

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4. Seatbelt buckle

-Then there is the seatbelt buckle which can be faulty. This will cause the annoying seatbelt warning noise to not go off even if your seatbelt is fastened. Surprisingly the new buckle is not that expensive, but you can also find someone with a diagnostic computer to deactivate this warning completely.

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5. AC system

-It’s also good to check the AC properly, because if one side is cooler than the other while the temperature is set to the same value on both sides, then this issue is usually caused by the heater valve which can clog and get stuck. In some cases it’s enough to disassemble and clean it but if this won’t help then you will need to replace it. To minimize the chance of this issue happening it’s good to occasionally turn the temperature on both sides all the way down, wait a little and then turn it all the way up to make the valves move. Since if you won’t change the temperature a lot then the valves won’t move that much + if you won’t change the coolant regularly then the debris in the coolant will clog the valve. So of course you should also keep the coolant clean, which means that you should change it completely at least every 4 years. Also make sure you do have clean cabin air filters → How to replace the cabin air filters video.

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6. Electronic parking brake

–Check the electronic parking brake which can occasionally seize up mainly if the owner not used it regularly, so at least engage and disengage it a couple of times

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7. Tail light condensation/water leak

-Mainly on the saloon models there can be an issue with the tail light condensation/water leak. This can be fixed by either replacing the black seal which is on the plastic cover → which is attached to the back of the light (on the picture below). Or if this wont help, then you can put silicone around the edges of the light-where the outer-red cover meets the plastic housing.

Avant / estate additional issues

Overall there are not that many issues as you can see, but if something seems like it’s too good to be true then it’s most probably not true, or something like that, so the Avant versions can have more additional issues as a bonus:

tailgate, wiper motor, leak

• The rear windscreen wiper motor can fail because of the washer fluid which will leak right into the motor-which will break completely. But this washer fluid wont leak only into the motor but also into the tailgate, so if nobody is going to fix this then the tailgate slowly starts to rust because of the accumulated washer fluid, beautiful. But even more beautiful scenario is, when you get water leak into the tailgate from the inner tail light seals since as they age they can let the water in too.

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washer fluid leaks

1. Interestingly the washer fluid can leak not only from the rear washer motor but also from the hose which is right next to the trunk lid hinge. This is more serious since the fluid will leak right into the amplifier, into the radio module and into the navigation system DVD module. All these modules are connected which means that even if one fails completely then your whole MMI system won’t work at all. However the only good thing is, that there was a recall specifically for this issue so most of these cars do have already fixed this hose – if the car has a dealer maintenance history of course.
2. And the last washer fluid leak can occur right under the driver’s seat. Right under the carpet is a plastic washer fluid hose which can leak. This leak is also not the best since you won’t even know about it until the carpet and the area under it will be soaked with the fluid, or until your bluethoot handsfree won’t work properly since the bluetooth module and also a wiring loom are next to his hose. The bluetooth module can be easily completely or partly ruined because of this leak. On the other side this leak can be easily fixed using a little bit of imagination and improvisation. All you need to do is cut out the plastic hose and find a smaller short random hose which you can connect to the plastic hose. And by the way, you need to remove the seat and some plastic surrounding trim to access this area.

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As a bonus the Avant version has another 2 age related cosmetical features which are related to fading.

-First of all, the inner rear lights on the avant version are made from a cheaper plastic, so in a lot of cases you can see that they are faded like on the picture below.

-But the rear inner lights are not the only thing which is fading in the rear of the avant version, since the rear glass edges are also fading, I mean what the fuck. I have seen this kind of glass fading in other cars as well, but not in a big scale like this. I have seen a huge amount of these A6 avants with this “feature”, and it looks like shit, what can I say?

Suspension

Let’s continue with the suspension which can be good but it can also ruin your day. There are 3 types of suspension in these cars:

• standard suspension

• s-line sport suspension

• adaptive air suspension

As in most of the other cars there are no extraordinary issues with the shock absorbers of the standard or the sport suspension, just check them for leaks of course. Also keep in mind that plenty of the owners complain that the sport suspension is very stiff so if you have bad quality roads around you then it’s better to choose a car without this suspension type.

The self levelling adaptive air suspension is on the other side a different story. You can adjust not only the ride height but also the stiffness of the shocks, so in comfort mode it is comfortable but in dynamic mode it gets noticeably stiffer. +In the Allroad models you can adjust the ride height a little higher than in the regular versions equipped with this suspension, but this of course doesn’t mean that it will magically become an off road vehicle…

The lifetime of the front air struts is approximately 10 years which means that after this point you are on borrowed time since they can fail at any time. Of course they can withstand even more than 10 years but mainly if the car was not used on winter salty roads, since not only the age but also the road salt reduces the lifetime of the air struts. All in all, don’t be that guy who has a 10+ years old A6 with an air suspension and who doesn’t have a clue that the air struts can leak at any time, because surprise, surprise, they can! A low rider A6 with a leaking air strut is not something which would cheer you up, because in this case you can’t drive it anywhere. The brand new genuine air strut costs a bit more than 1 600 € which is a lot, but it is gonna withstand at least another 10 years. Of course you can also buy a well known aftermarket part which is still not the worst idea, but buying a no name aftermarket or a Chinese air strut is definitely a bad idea, unless you want to be a test dummy.

While the front air struts are a single unit – so the shock absorber and the air strut is combined, then in the rear they are separated – so the air strut is a single unit as well as the electronic shock absorber.

The rear air struts usually won’t last that long as the front, which means that they can start to leak earlier than 10 years, but luckily the rear air struts are not very expensive. On the other side the rear electronic shocks are really overpriced + after 200 000 km or even before this mileage point they will leak. So if you are buying an A6 which is equipped with the air suspension then check the rear shocks for leaks, because one new genuine electronic rear shock absorber costs more than 800 €, and that really is a lot. Unfortunately currently there is no well-known aftermarket company which would make these rear shocks. On the other side there are companies which are selling cheaper refurbished rear shocks and there are also those Chinese made shocks available of course.

Usually if you got an early leak in the system then the car will drop overnight in dynamic, automatic or comfort settings, but if you leave it in the higher modes like: allroad or lift then it won’t drop.

Also keep in mind that the suspension height sensors can seize up over time – causing various creaking noises (eventually they can also break), so after buying it’s good to clean and re-grease the ball joints on them.

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The other suspension components can easily withstand more than 200 000 km, only the front upper control arms and the front drop links can be worn earlier + the wheel bearings can fail too, but of course check all the suspension components visually and listen for weird sounds during driving.

“Because of the engine which is mounted after the front axle the handling of this car in corners is, well, not awesome, which means that the rival of this A6 – the BMW 5 series E60 has much better handling with much better weight distribution and with better steering response/feel as well. On the other side because of the Quattro 4wd system, because of the complex suspension design and because of the bigger weight, the stability of this A6 on the highway or on bad quality roads even at higher speeds is very impressive. And it doesn’t matter if it’s raining, snowing or if there is an apocalypse outside. So while in bad weather everybody will go in the right lane on the highway, you can go faster in the left lane without any worries (of course for this kind of an artistic performance it’s necessary to have good quality winter or summer tires, ok?).”

Petrol engines

2.4 V6, 4.2 V8

From the petrol engines the most reliable is the 2.4 l naturally aspirated V6 unit. It doesn’t have direct injection and it doesn’t have a turbocharger either so it is simple and reliable. On the other side it’s definitely not powerful (although for a regular/casual/calm cruising it will be ok), and the high mileage examples (250 000 km or more) can suffer from smaller or bigger oil consumption.

Then there is the second most reliable engine which is the older 4.2l V8, again, not equipped with the direct injection. In this case it is definitely powerful enough but it’s also much more prone to different oil leaks (valve cover gaskets, oil pan, oil filter housing etc.) so definitely check for leaks and for burnt oil smell around the engine + have some extra money left since these oil leaks are sometimes not the cheapest to repair.

Other engines

All the other engines are equipped with direct injection so you can expect:

• the well-known carbon build up on the intake valves (misfires, loss of power)
• faulty injectors (misfires, loss of power and sometimes they can leak causing funny stuff which Im not interested to explain since nobody is paying me for this)
• faulty HPFP causing: bad/rough engine start and rough idle, slight external or internal fuel leak.

2.0 TFSI

The 2.0 l 4 cylinder TFSI is actually not a bad engine and with regular maintenance in can easily reach 300 000 km, but of course the abused examples will have problems with the turbocharger or with excessive oil consumption + in higher mileage cars it’s also good to check the camshaft follower which is connected to the high pressure fuel pump. This part is cheap but it can be worn out and cause damage to the camshaft, fuel pump or it can send metal particles into the cylinder head. Also check for fuel leaks from the high pressure fuel pump because it will leak fuel from the solenoid valve as its getting older! high pressure fuel pump fuel leak location video

2.8 FSI, 3.0 TFSI

Then there is the 2.8 l FSI and the 3.0 l TFSI. These engines are not the worst but they can have the already mentioned direct injection related problems + sometimes leaking water pump + mainly the 3.0 l TFSI can have smaller or bigger oil consumption.

3.2 FSI

The 3.2 FSI V6 again doesn’t have any huge issues except the direct injection related stuff and the various oil and coolant leaks. For example the valve cover gaskets, the oil filter housing or the rear timing chain covers will leak at some point. You can fix these leaks without removing the engine, although it’s definitely not always easy and in some cases you have to disassemble a lot of things to fix them. + there is one high pressure fuel pump which will leak fuel from the solenoid valve as its getting older! high pressure fuel pump fuel leak location video

4.2 FSI V8

Lastly there is the 4.2 FSI V8. This engine is also affected with the well-known direct injection flaws and it will also-in a lot of cases-leak oil and coolant. However in this case because of the lack of space you have to remove the whole engine if you want to fix certain leaks – like for example the the rear timing chain cover leak or the spark plug tube leak. + There are two high pressure fuel pumps which will leak fuel from the solenoid valve as they are getting older! high pressure fuel pump fuel leak location video

+The variable intake manifold in this engine is a complicated piece of shit actually. And why? Well, because of the plastic insides mainly. But long story short:

• the inside of the intake manifold gets dirty over time
• the plastic bits in it are gonna get brittle – break – and fall apart (eventually the bits can be sucked into the cylinders IN THE WORST CASE-so rarely I guess)
• the 2 electric actuators mounted on front of the manifold can fail too

The only good thing is that these issues are gonna occur usually just after 200 000 km – 250 000km.

4.2 FSI → How to replace the engine air filter and the spark plugs video

Coolant leak which will kill this engine

-Behind the engine there are the timing chain covers. These covers do have a hole in them thru which the coolant flows. This would be fine, but it’s not. It’s not fine, since the coolant seal on these covers can fail and let the coolant leak directly into the engine-into the oil. Long story short: If you don’t catch this early then you will end up with a destroyed engine.

Other stuff

can adjustment solenoids

All these petrol engines can have faulty camshaft adjustment solenoids and these parts have been actually revised several times. They can get stuck because of long oil change intervals – and in this case you get fault codes for the camshaft position, misfires or fluctuating/bouncing idle. These solenoids can leak oil as well, but in this case there is no need to replace them completely – you just need to change a small o-ring on them.

vacuum leaks

Vacuum leaks can occur on all the petrol engines, so be ready for cracked plastic or rubber vacuum hoses and faulty PCV. (vacuum leaks symptoms: slight misfires, uneven engine running, eventually check engine light + the faulty PCV can cause oil consumption too)

The petrol engines have to be perfectly smooth at idle and during acceleration as well.

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Long story short: if you are buying a petrol engine then make sure that you start the car when it’s cold and check for shaking/uneven idle. This is caused by misfires which can indicate excessive carbon build up, faulty ignition coils, faulty injectors or other issues.

Don’t forget to check also the coolant while the engine is stone cold – it has to be light red and clean without any kind of oil traces or oil smell. If there is oil in the coolant, then the engine most probably has serious issues like leaking head gasket or cracked cylinder head, and believe me, you don’t want to deal with any of that shit, just run away.

All petrol engines can have broken exhaust flexible pipes.

Diesel engines

The diesel engines don’t have unexpected major issues except the 2.0 l TDI 4 cylinder.

2.0 TDI

This smallest diesel engine with the older PD injection system can have problems with the worn oil pump drive which can fail – in this case the engine will lose oil pressure and this will most probably kill the turbocharger and it can of course do other more serious damage too – this depends how fast you shut off the engine after the low oil pressure warning comes on. The oil pump drive can be worn after 100 000 km or just after 200 000 or 300 000  km, so nobody knows when exactly but you can check the condition of it after you remove the oil pan. By the way even the newer 2.0 l units with the common rail injection can have this issue but not that often as the older versions. Replacing the complete oil pump drive module can cost up to 3500€, but this obviously depends on the actual damage so it’s a lot cheaper to replace it preventively. So I would just stay away from at least the older generation 2.0 l TDI engines because they can have not only worn oil pump drive, but more often faulty injectors + there are more often cases of cracked cylinder heads and some other not interesting stuff. And if we take into consideration that most of these engines have nowadays more than 250 000 or 300 000 km then it really is not a good idea to recommend them.

2.7 TDI, 3.0 TDI

Then there is the 2.7 l and the 3.0 l TDI. Both of these engines are technically speaking basically the same so they have the same issues:

-first there are the intake manifold flaps which can sometimes fail. The flaps can be stuck, loose or the actuator motors can be faulty. In this case you get only a check engine light-so the car will drive fine. The whole intake manifold part is obviously expensive (around 500 €/side) but you can find repair kits for a much reasonable price.

-then it’s also good to check and eventually replace the crankshaft pulley vibration damper mainly in cars which were used on winter salty roads. Since over time the inner part of the pulley will rust out and separate from the outer part. This will leave you stranded because the accessory belt will jump off-so it’s better to check this pulley before you will wonder what the hell happened !!

And the last two things related to these 6 cylinder engines:

–the high pressure fuel pump has a separate belt and a tensioner. Most of the owners don’t even know that there is a separate belt for the high pressure fuel pump, so it’s good to replace these two parts if the car has more than 200 000 km or 10 years.

-lastly, if you are buying a car which has around 300 000 km then be prepared to replace the alternator since its lifetime is approximately the already mentioned 300 000 km

When it comes to injectors, yes they can be faulty on all the diesel engines, but usually just after 200 000 km. Of course they can last way over 300 000 km as well, but this depends on many different things including the fuel quality used or the year of the engine. But all you need to know is, that if you got faulty injectors then you will most of the time notice a couple of signs like the: occasional light grey smoke from the exhaust while acceleration/or at idle, issues with starting the engine, a slightly bouncing idle when the engine is warmed up, or an increased fuel consumption.

CP4 HPFP

The newest diesel engines made from late 2008 (so the 2.0 TDI 125 kw, 2.7 TDI 140 kw, 3.0 TDI 176 kw) are equipped with the infamous Bosch CP4 high pressure fuel pump which can sometimes fail even after 150 000 km (MOSTLY JUST in the Eastern EU because of the different fuel quality). If it fails it will throw small metal particles in the fuel system, thus destroying the injectors, the HPFP + these particles can contaminate the fuel tank as well. So in this case the whole or just certain parts of the fuel system including the injectors and the high pressure fuel pump has to be replaced and eventually cleaned. Repairing this can cost up to 4 000 €-independent mechanic, up to 6 000-7 000 € at the dealer.
More information about this failure in this BMW X5 article.

The 4 cylinder engines are equipped with a timing belt so just make sure that it was replaced in time. Also keep in mind that you should replace not only the timing belt but also all the tensioners and you should definitely install new tensiononer screws as well, because there are cases when the owners re-used the old screws and the screw broke causing a serious engine damage + of course replacing the water pump preventively is a good idea as well.

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Timing chain

The other engines are equipped with timing chains. The tensioners and the plastic guides can be worn + the chain can be stretched, but usually just after 200 000 km – in this case you get the well-known short rattle at cold start.

The funny thing is, that there aren’t many catastrophic engine failures because of the timing chains at least amongst the diesel engines. Because the petrol engines are actually more prone to a chain mechanism failure in which the chain mostly skips a tooth making the engine run like garbage or the plastic guides crack causing a rattling noise and other funny stuff. But at the end of the day it’s up to you, if you got the short rattle then you can wait or you can preventively replace the tensioners and the chain. The timing chains are located on the back side of the engine so this is not the cheapest repair since you have to remove the engine to change them.

Generally speaking at 300 000 km its definitely good to preventively replace the chain if it was not replaced in the past.

By the way if you got one of the 6 cylinder engines and if you have around 200 000 km or less than 200 000 km, but you hear the rattle then you can first replace only the upper chain tensioners which will solve the rattling and this will prevent the excessive wear of the chain+the upper tensioners can be replaced without removing the whole engine. (how to replace the upper chain tensioners 3.2 FSI)

Transmissions

This A6 can be equipped with the 6 speed manual gearbox or there are 2 types of automatic transmissions.

Manual

-The 6 speed manual is reliable, however check the clutch properly before buying – it should operate smoothly without any kind of strange noises, vibrations or shuddering. If you are buying a diesel engine with the manual gearbox then have extra money left for the Dual mass flywheel which can be worn. In this case it can, except the already mentioned symptoms, also cause vibration at idle or metallic clattering sounds from the gearbox area. To extend the lifetime of the dual mass flywheel you should always release the clutch calmly rather than releasing it suddenly and never let the engine to operate at low RPM – so make sure that while driving the RPM stays above 1 400 RPM.

(new clutch + DMF – 2 500€ at the dealer, new DMF only – 1 000€)

Tiptronic

-From the automatic transmissions the regular 6 speed Tiptronic is the most reliable although after 250 000 km you should be prepared to replace the torque converter since it can be worn out mainly if the previous owner never changed the gearbox fluid. + of course check it properly before buying

Multitronic

-The Multitronic is a CVT gearbox which is still not very reliable, although it’s at least more reliable than in the previous generation of this A6. Long story short with regular oil changes and with a regular/not aggressive driving style it can withstand even more than 200 000 km, but of course after this mileage point the lifetime of the gearbox starts to be questionable. Without regular oil changes and with more dynamic driving it can fail after 150 000 km or even before this mileage point.

If you really want the multitronic gearbox then check it properly before buying. If it’s shuddering or if it’s not working completely smoothly then run away and find another car. (the price for repairing the multitronic gearbox usually starts at 1 900€)

All of the automatic transmissions have to change gears without shuddering, strange sounds, fluctuating RPMs and they have to be smooth and especially the Multitronic has to work perfectly smooth all the time.

Quattro

The Quattro is still that good, old school, mechanical and very reliable permanent 4WD system. Usually it doesn’t have issues even in high mileage cars and it doesn’t require bigger attention/care. HOWEVER:

• it’s very important to have the exact same tires with the same tread depth on the front as well as on the rear axle

• it’s good to occasionally change the oil in the front and rear differentials and even in the transfer case (replacing the transfer case oil can help to eliminate the low speed “quattro growl”)

• in cars with more than 250 000 km it’s good to check the propshaft for excessive wear → check for vibrations or shuddering at hard acceleration from stand still or for a vibration at highway speeds which can indicate worn propshaft.

To summarize things up:

• the simplest most reliable version is a saloon/sedan model with the 2.4l petrol engine and with the manual gearbox or with the 6 speed Tiptronic gearbox
• the 2.7 TDI and 3.0 TDI engines are very good but keep in mind the issues they can have after 200 000 km
• find a good independent mechanic
• keep at least 2 000 € for the possible repairs

But if you are buying a car which have more than 200 000 km or if you are buying a V8 engine then you should keep at least 4 000 €. And to top of that, if you want a car with the air suspension then you should keep an additional 3 000 €, which means that if you want a V8 with an air suspension then you should keep 9 000 €, unless you can fix your own stuff of course.

And if you have personal experience with this car or more information about it, then you can write it into comments!