RS246.com Forum :: The World's #1 Audi R, S and RS Enthusiast Community

Following our factory visit to Neckarsulm earlier this year, and having received zero comments with their staff, I contacted Audi UK upon my return to ascertain their position re the issue of carbon build-up, This is their official response:


Thank you for your enquiry regarding the carbon build up in the Audi RS4. Please accept my apologies for the delay in getting back to you. No discourtesy was intended. As you will be aware your concerns were passed onto our Head of Customer Services, Richard Starkey.

Richard has now had the opportunity to discuss your concerns with Audi AG on a recent visit.

Unfortunately, Audi Germany does not recognise carbon build up as an issue, as they do not see any potential performance or mechanical problems arising from this. They have advised carbon is a bi-product of burning fossil fuel which is a natural occurrence on all petrol engines. Therefore Audi AG has ruled out any fixed support towards the cleaning of the RS4 Engines to remove any carbon build up.

They have further advised that it is for Audi UK to investigate this on a case by case basis and therefore any support is assessed individually.

I appreciate that this may not have been the response that you were hoping for, but trust I have clarified our position.


So that's that! Or is it??? It's obviously being dealt with on an individual basis which ties in with the stories of certain owners having clean-ups FOC and others with some form of contribution from Audi UK. Guess it depends on individual circumstances.

However anyone in their right mind can state that this scale of build up would not cause a problem is beyond me!



Obviously the first point of call is your dealer who should then take it to Audi UK for their response. All I can say is 'Good Luck'!

..claim by claim is usual spiel for only dealing with problems as they arise rather than doing a recall/service campaign as they know a relatively small number complain.

Someone mentioned changing to 5w/40 fully synthetic rather than the 5w/30 stuff they use for long life because the 5w/30 runs hotter and vapourises more readily which can cause what we see in the pic.

Forgive me if this particular point has been discussed again and again but curious to know an expert's (i.e. not mine) view on this?

I am off long life and on 5w/40 at 5k intervals.

Why is 5w/30 better than 5w/40?

this thread implies 5w/40 is better yet it's cheaper!

http://audisrs.com/archive/5w-30-5w-40. ... 12405.html

forgive me if this is seen as OT

Are they your valves caldy? If yes, what was your reason for taking the head off.

Well done Caldy for seeking an answer and spot on Terry - it's cheaper to deal with the minority on a case by case basis than admit an issue, lose face and recall all cars.

You can throw all the forumlas in the world at this to prove it's not at the very least a 'potential' issue but pictures speak a thousand words....What's the history of the car in the pic?

As for the thicker oil, Afaik the idea is it helps reduce seepage around then piston rings

I ran my car for 2k after cleaning on this spec oil and a closed off inlet manifold and even then build up was present upon reopening??!!

Thats horrific is it really an rs4 head? As someone who has read the endless threads on the subject and bit the bullit and paid to have them cleaned,i can honestly say there was very little power difference in the dyno plots until very high up the rev range and the gains then i think were down to floed n ported inlet manifolds not carbon removal,im more inclined to study the particular cars drivers styles and usage to get to the cause of build up as bad as that,my car was commented on as not being bad,it gets warmed up well run on good oil and its throat cleared when im in the correct situation,i dont use the car the car for work ie motorways and it does it share of short town work too,maybe the cars with build up as bad as this need reving harder more often or a good spirited on a regular basis? Im not sure oil has so much to do with it but im no expert and would listen to ideas

iirc that car (uncleaned saloon) was run head to head, same day, same road against a car (avant) with >70k miles (never cleaned)
no performance difference, within a meter or so either way, multiple gears

the car was then cleaned by the dealer, heads off,obviously (has ~40k miles or so)
the test was re-run...again, no difference
despite the cleaned saloon having: less weight, a plug change and heads off cleaning/decoking...
no difference, iirc, 6 runs...
and wouldn't a car with 74k like the avant have WORSE deposits, or at least as bad, if it was never cleaned?
yet, same speed as the lighter, tuned up, cleaned car...
all one can conclude is deposits are not the issue some think (or hope) they are...

isn't it remotely possible that Audi is correct? (as are BMW, AMG, Ferrrari, Porsche who are all going to DI?)
the physics/engineering, imho, bare their position out...

the reason it is case by case is that in extreme cases, it is caused by the failure of another system...the average car has no issues...
but even in this extreme case, no performance delta, before or after
by far the most convincing arguement I've seen to date

it's funny: I was banned on other forums for refuting the assertions of others that Audi considered it an 'issue' and acknowledged the 'problem'
when the exact opposite is true...
they went as far as to actually make posts they claimed were directly from Audi...

whether one agrees or not as to the if it is an 'issue' , it should at least be clear Audi does not consider it one and that is their official position...

To be fair Audi are goung to say that regardless to avoid a que of rs4 r8 etc etc on there forecourts demanding expensive carbon removal,When you get to this level of management @ any company they start to behave like polititions!!!!!! Doug @ mrc commented on my plugs when changed were burning a little differently from one cylinder to another,due to build up form and shape i dare say (you can see a difference in the tips of the ones in the pics also) its not good to have that situation on a highly tuned v8 is it? or any engine for that matter,but seems the affects are barely noticeable in performance but must get to a point were you risk damage if it builds up too much?

I totally disagree that the effects are barely noticeable. My engine was so badly choked up that one of the cylinders was down on compression due to a valve not able to seat properly due to deposits. No one can tell me that isn't affecting power because it quite simply is. End of.

As i said "but seems the affects are barely noticeable in performance BUT must get to a point were you risk damage if it builds up too much? Your car Karl seems to have unfortunatley dropped into the latter.Im wondering if continual short trips stuck in city centres etc is partly to blame on the cars that have suffered the more extreme cases of build up such as Karls. Something is having an effect on build up fuel..oil quality..running temps...revs/airflow.... Ive noticed on a few vids of mrc cars on the rollers that out of one exhaust at high rpm you occasionally get a puff of black sh%t come out which i presume is carbon? as it hadnt hit the limiter yet it wasnt un burnt fuel.I dont know just my little theory somewhat backed up by my own experiance of before and after cleaning etc and how my car is used.

This issue is far from unique to Audi or high perfomance cars,a pal of mine has had to strip and clean inet vanes on his 530d with only a low mileage on it,these engines are a victim of curcumstance,the greenies and government want low emmisions but we still want high performance cars so........... Ultimately though its very worring that odd cars could coke up so bad they require heads off to clean and re seat valves,you shouldnt be faced with this situation on a fairly new expensive car that has been maintained according to service schedules under any curcumstances but in reality we are,but there a potential issue with every high performance car lurking under there somewere?

caldy wrote:Unfortunately, Audi Germany does not recognise carbon build up as an issue, as they do not see any potential performance or mechanical problems arising from this.

...............what woud they call an MOT failure then?

I this the reason for mot failure then i take it Pad125?

karl wrote:I totally disagree that the effects are barely noticeable. My engine was so badly choked up that one of the cylinders was down on compression due to a valve not able to seat properly due to deposits. No one can tell me that isn't affecting power because it quite simply is. End of.

A more accurate statement may be that the effects of carbon on a normally operating engine are barely noticable. Given it was significantly noticable in one cylinder on your car Karl that would perhaps lead to conclude there was a faulty part in that cylinder.

There is 'data' out there for all to see that has dismissed most of the areas from which people believe CB is attributable to. Poorly designed cyclonic separators; put a catch can instead and oil barefly enough to cover your thumb tip is collected at most. Valve overlap; there is data to suggest this isn't the case.

Perhaps a lot has to do with valve seals and the amount of oil that seaps through them in warm up phase. If they have a lot of tolerance in them when cold seapage may be higher than at operating temperature. This oil that seap collects on the valves and in the IM but if at low speed or stop start motoring / communting not enough airflow gets into the engine to blow this off towards the cyclonic separator. Combine this with lots of high revving early in the warm up phase which may push more oil through the valve seals before the shore up so to speak with heat in them the higher amount of oil present may accelerate the level of CB in the IM.

Just a wild theory of mine based very loosely along the lines of F1 technology. If you consider an F1 engine has to be pre heated and the oil warm and passed through before turning over because there is such tight tolerances to achieve the 18,000+ rpm they can run to. Ours are high revving but have to have low tolerances for cold start purposes maybe this is when the most amount of oil gets into the IM?

pad125 wrote:

caldy wrote:Unfortunately, Audi Germany does not recognise carbon build up as an issue, as they do not see any potential performance or mechanical problems arising from this.

...............what woud they call an MOT failure then?

That may be categorised in the grey area of what is 'excessive' carbon build up and what is 'normal' and if 'excessive' why is it so?

As has been said they aren't going to do a mass recall due to costs so it is a positive that they may well look at this on a case by case basis although that in itself is not pain free process.

lengster1 wrote:I this the reason for mot failure then i take it Pad125?

Yes!