Carbon Buildup on the 3.0 TFSI Pics!

[mr shickadance]

one other thing to consider i suppose would be if it was a catalyst reaction, once the valve is 100% saturated wouldn't the carbon build up halt as there is no more material left in contact with the valve in question?

look, obviously you have done far more research on it than i have, but it just seems like since this is cross-platform, cross-make issue only relating to direct injection engines, that exploring on just audi's engines seems like a niche way to derive conclusions from.

but i suppose i am happy there is at least a few people looking into this, the speed3 issue was solve by the egr delete, but they used a different system to pass emissions, and I think the b7'rs had a write-up for a carbon build up solution that essentially did the same, but there was no long-term evidence suggesting it was curing the problem, but the idea and the logic were there, the speed3 was confirmed, and therefore the only reason i used it as an example.

[achilleas101]

From other related tests I have always advocated the use of 502/505 spec oil (genuine full group IV or better base stocks only) on TFSI engines rather than the 504/507. 504/507 is marketed as superior oil but this is not the case. Many important ingredients were removed and replaced with inferior and more expensive alternatives in order to protect emission control components, such as the DPF, on VAG diesel engines. This doesn’t apply to VAG gasoline engines but to simplify long life oil changes 504/507 is now recommended across the board.

Most of this stuff is definitely beyond my understanding, so please excuse me if this question was addressed and i didn't get it. But i'm confused by this statement in bold above. did you mean to say "long life oil changes 504/507 is noT recommended across the board"?

and if so, are you basically saying shorter oil change intervals are better?

[Moose201]

I am trying to avoid recommending particular oils as it is likely to open a can of worms and series of questions that I don't want to get into right now. My background is fuel modification, tribology and engine tuning in that order of experience. I am in the trade but not a registered trader on this forum (and don’t intend to), so I don’t in any way want to come across as pushing any products. I am here as a fellow S4 owner that can hopefully add value and nothing more.

I will mull it over and see if I can come up with a list. One thing I will say is that M1 would never be seen in my car. The other issue is that we know factually that oil manufacturers adjust blends for different countries/regions, to achieve market price expectations.

A list would be appreciated. Curious though why you would never use M1?

[audistealth]

A list would be appreciated. Curious though why you would never use M1?

+1

[mojangles69]

A list would be appreciated. Curious though why you would never use M1?

+ 2!

No need to push a particular product, AndyUK. In our eyes, you are simply a fellow S4 owner recommending a or several different possible oils, that in your experience and through your research, would be best for our vehicles!
And again, thank you for all your insight thus far, you've been more than informative!

[AndyUK]

Very good point. The build-up proliferates because the carbon remains chemically active.

one other thing to consider i suppose would be if it was a catalyst reaction, once the valve is 100% saturated wouldn't the carbon build up halt as there is no more material left in contact with the valve in question?

look, obviously you have done far more research on it than i have, but it just seems like since this is cross-platform, cross-make issue only relating to direct injection engines, that exploring on just audi's engines seems like a niche way to derive conclusions from.

but i suppose i am happy there is at least a few people looking into this, the speed3 issue was solve by the egr delete, but they used a different system to pass emissions, and I think the b7'rs had a write-up for a carbon build up solution that essentially did the same, but there was no long-term evidence suggesting it was curing the problem, but the idea and the logic were there, the speed3 was confirmed, and therefore the only reason i used it as an example.

[AndyUK]

It's not you. After reading it again it’s clear I didn’t word it very well.

To clarify:

504/407 is a low-SAPs long-life oil with a good proportion of the good stuff taken out (such as sulphated ash) in order to protect diesel particulate filters on diesel engines. In Europe at least it seconds as the preferred long life oil for gasoline TFSI engines. Many dealers even use it on annual services as it's easier to stock one lube. 504/507 appears to have become the de facto oil across the range.

In my professional opinion a high-end 502/505 full-SAPs oil provides improved short and medium term benefits including improved protection and most importantly lower oil consumption on TFSI engines. The only downside is that it won’t last as long

The reason I originally posted this is because 504/507 is regularly touted as superior oil for TFSI engines. I don’t agree with this.

Shorter oil changes are simply good insurance but I don't have any direct evidence to suggest this reduces deposit build-up on the intake valves.

The engine in my S4 consumes less than 200ml per 5,000 mile oil change.

Most of this stuff is definitely beyond my understanding, so please excuse me if this question was addressed and i didn't get it. But i'm confused by this statement in bold above. did you mean to say "long life oil changes 504/507 is noT recommended across the board"?

and if so, are you basically saying shorter oil change intervals are better?

[AndyUK]

Sorry, don't want to go there but I will say this. When you have seen as much of the oil market as I have, met with manufacturers, discussed additives packs with chemists etc. etc., it becomes clear that the consumer oil market is just one big marketing competition.

Once you have determined the correct/recommend specification you should ask the following question rather than make a decision based on brand.

“What am I getting for my buck and who is offering the greatest value for every buck I spend?”

In other words, invest in the greatest value group IV+ base oil rather than pay inflated prices for over-marketed group III oils.

A list would be appreciated. Curious though why you would never use M1?

[mojangles69]

Sorry, don't want to go there but I will say this. When you have seen as much of the oil market as I have, met with manufacturers, discussed additives packs with chemists etc. etc., it becomes clear that the consumer oil market is just one big marketing competition.

Once you have determined the correct/recommend specification you should ask the following question rather than make a decision based on brand.

“What am I getting for my buck and who is offering the greatest value for every buck I spend?”

In other words, invest in the greatest value group IV+ base oil rather than pay inflated prices for over-marketed group III oils.

AMSOIL is what keeps showing up on Google. And this is the oil they recommend, on their website, for our B8 S4's.

It is not a Full-SAP but a Mid-SAP oil. --> http://www.amsoil.com/shop/by-produc...?code=AFLQT-EA

Here is the Full-SAP oil. Interestingly enough, it's cheaper! --> http://www.amsoil.com/shop/by-produc...?code=EFMQT-EA

Homepage --> http://www.worldsbestoil.ca/oilforDieselCarsTrucks.php

Andy, give us a simple "thumbs up" if these meets the recommended criteria!

[AndyUK]

One of our European distributors is also a distributor for Amsoil so I will try and get hold of the ingredients disclosure and let you know.

Mid-SAPs = more expensive? YES! Low-SAPs even more expensive. This is because they are replacing the good stuff with more expensive alternatives to protect a component (DPF) no gasoline vehicle has!

I have to refrain from invalidating customers when they tell me that they have spent $100 on the best 504/507 specific for their Audi TFSI. I then ask how much oil it burns. “Um, quite a bit but it’s a great oil”.

AMSOIL is what keeps showing up on Google. And this is the oil they recommend, on their website, for our B8 S4's.

It is not a Full-SAP but a Mid-SAP oil. --> http://www.amsoil.com/shop/by-produc...?code=AFLQT-EA

Here is the Full-SAP oil. Interestingly enough, it's cheaper! --> http://www.amsoil.com/shop/by-produc...?code=EFMQT-EA

Homepage --> http://www.worldsbestoil.ca/oilforDieselCarsTrucks.php

Andy, give us a simple "thumbs up" if these meets the recommended criteria!

[mr shickadance]

so what is the oil you trust to put in your car?

[visualguy]

I'm curious about why the severity of this problem varies so much from engine model to engine model. For example, Porsche naturally aspirated DI engines (A91) don't seem to suffer from it nearly as much. Also, some Audi DI engine models suffer from it much more than others. Assuming the root cause is the oil reacting with the valve material, what explains the big differences between engine models?

[mojangles69]

One of our European distributors is also a distributor for Amsoil so I will try and get hold of the ingredients disclosure and let you know.

Mid-SAPs = more expensive? YES! Low-SAPs even more expensive. This is because they are replacing the good stuff with more expensive alternatives to protect a component (DPF) no gasoline vehicle has!

I have to refrain from invalidating customers when they tell me that they have spent $100 on the best 504/507 specific for their Audi TFSI. I then ask how much oil it burns. “Um, quite a bit but it’s a great oil”.

LOL! I love it. What we need and is the best option for our engines is the cheapest version of the oil and the most expensive version is the worst option bc they take out the good stuff and replace it with more expensive alternatives that do us no good. Perfect

So glad you joined this thread AndyUK and spoke up! Learning a lot!
Gotta love marketing!

[Moose201]

so what is the oil you trust to put in your car?

+1

[AndyUK]

It's a custom blend.

so what is the oil you trust to put in your car?

[AndyUK]

There are many variables. I have listed some below with the #1 being the most important and working down from there:

1. Valve material
2. NA or forced induction
3. Driving style
4. General intake/valve/engine design
5. Lubricant

The 2.0T, 3.0T or 4.0T will never suffer as much as an NA engine. Interestingly, Audi appear to be moving to FI with all of its gas engines. Emissions is one factor but....

My knowledge of Porsche engines is limited so unable to comment.

I'm curious about why the severity of this problem varies so much from engine model to engine model. For example, Porsche naturally aspirated DI engines (A91) don't seem to suffer from it nearly as much. Also, some Audi DI engine models suffer from it much more than others. Assuming the root cause is the oil reacting with the valve material, what explains the big differences between engine models?

[Moose201]

Appreciate all the info and realize that you don't want to comment on M1. Would still be helpful if you could mention a few off-the-shelf oils that should be considered. Thanks.

[SwankPeRFection]

Sorry, don't want to go there but I will say this. When you have seen as much of the oil market as I have, met with manufacturers, discussed additives packs with chemists etc. etc., it becomes clear that the consumer oil market is just one big marketing competition.

Once you have determined the correct/recommend specification you should ask the following question rather than make a decision based on brand.

“What am I getting for my buck and who is offering the greatest value for every buck I spend?”

In other words, invest in the greatest value group IV+ base oil rather than pay inflated prices for over-marketed group III oils.

Are you insinuating that M1 is expensive? Because in our country, it's the easiest to find and least expensive of them all. Perhaps it's different in the UK. Look, I know you don't want to get in a oil pissing match here and hopefully people will avoid that, but I do want to know if some of your logic on this is also region based? I ask this because like you not wanting to put M1 in your car, Castrol won't be put in mine. The same thing would go with other off-brand ones because they are harder to get and if for some reason the specification ins't on the bottle (even though it's a better oil), the manufacturer WILL GET in a pissing match should something happen. While I can't speak for carbon buildup (even on my B7 A4), I will say that I've always used M1 in all my cars and they've all survived until 100k+ miles with no issues. It just seems to work and it sure is easier to find than the Redline oils I used to use years ago.

[gringoloco2000]

I found this link in an old oil thread. I know the list is a little dated, but I found it interesting that Amsoil is not listed anywhere. Maybe it was branded differently when this came out?

http://microsites.audiusa.com/ngw/09..._1997-2010.pdf

[mr shickadance]

It's a custom blend.

what brand of oil that you can buy would you put into your car.

[BoostEasy]

Yes, It has been known for while to be from the valve guides and this is part of the design. What is new is the observation of a catalytic reaction between the oil and valve material.

Thanks Andy.

To be clear, I wasn't suggesting I discovered anything that OEMs probably didn't know, but rather that it wasn't common knowledge on car forums I frequent.

[visualguy]

There are many variables. I have listed some below with the #1 being the most important and working down from there:

1. Valve material
2. NA or forced induction
3. Driving style
4. General intake/valve/engine design
5. Lubricant

The 2.0T, 3.0T or 4.0T will never suffer as much as an NA engine. Interestingly, Audi appear to be moving to FI with all of its gas engines. Emissions is one factor but....

My knowledge of Porsche engines is limited so unable to comment.

Even if we limit ourselves to naturally aspirated engines, there's a big difference between engine models... I mentioned Porsche, but even if you limit to Audi, there's a big difference in susceptibility to carbon buildup between the older 4.2 FSI (RS4, S5) and the new one (RS5). Do they use a different valve material? Something different in the design of the engine? It's pretty interesting... Too bad car companies aren't saying anything about this whole topic of intake valve carbon buildup.

[AndyUK]

I agree but unfortunately I don't have all the answers - wish I did. I'm not aware of any significant difference in valve materials across the Audi DI range.

We were hoping to establish more common denominators with regards to the speed and degree of build-up but with the many variables involved this takes time and money.

Even if we limit ourselves to naturally aspirated engines, there's a big difference between engine models... I mentioned Porsche, but even if you limit to Audi, there's a big difference in susceptibility to carbon buildup between the older 4.2 FSI (RS4, S5) and the new one (RS5). Do they use a different valve material? Something different in the design of the engine? It's pretty interesting... Too bad car companies aren't saying anything about this whole topic of intake valve carbon buildup.

[BoostEasy]

FWIW, I did a little checking and it appears the low-SAPS oil was developed to protect diesel particulate filters AND modern catalytic converters.

eg http://www.oelcheck.de/en/knowledge-...ring-2010.html

It would appear that "Phosphorus and sulphur are highly poisonous to catalytic converters".

I'm no expert but that phrase came up fairly often in internet searches.

Maybe it's more of a question of degrees vs black/white re using low SAPS or not in a gasoline engine or perhaps there are differences in catalytic converter materials so this doesn't apply to all of them.

[Deckdout2]

Seafoam! hahahaha

[AndyUK]

Hi SwankPeRFection, from my short time on this board I respect you and the input you provide but I don't like the term "insinuating" as it implies I am trying to be underhand or derogatory in some way. I assure you that I am not and the moment readers think that is the case I no longer wish to contribute.

I am just trying to give some insight without putting all cards on the table as I also have a reputation and career to think off.

Did I get it wrong with the M1 comment? Possibly. This is my dilemma:

The ingredients and in particular, the base stocks vary considerably between regions due to varying market demands and conditions. Add this to the fact that manufacturers continue to move the goal posts so anything I say or recommend may not only leave me open to litigation but in 6 month’s time when someone else reads what I wrote, there is a good chance that it is no longer factual. Also, there are so many brands that it is impossible to keep up to date with who is using what. Then there is the issue of most ingredients being non-haz and therefore do not have to be declared on MSDS, so obtaining formulations is very difficult. The key is matching the correct oil to the engine type, engine demands, climate, driving styles etc. against your requirements with regards to price, performance and level of protection. Sometimes this can be achieved with off-the-shelf oils and sometimes it requires a custom blend or use of oils plus additives.

My initial response to the use of M1 was based on the UK market in general. I am not sure what you pay in the US? It also depends on what M1 product you are using or have used? If you can provide a link to what you use I can take a look and possibly provide a more informed view.

I would like to put the carbon issue back into context for the S4 and S5 models. Firstly, being of FI design the build-up is generally not that bad. Secondly, being FI means the effect of the carbon on performance is minimal. Therefore, significant running problems or warning lights are likely to be very rare except for abused and/or high mileage examples. You are not aware or inconvenienced by the issue to the degree it is actually not an issue.

Contrast this to the RS4 where the build-up is much more prolific and being NA the impact on performance much more severe. It’s a double whammy.

Are you insinuating that M1 is expensive? Because in our country, it's the easiest to find and least expensive of them all. Perhaps it's different in the UK. Look, I know you don't want to get in a oil pissing match here and hopefully people will avoid that, but I do want to know if some of your logic on this is also region based? I ask this because like you not wanting to put M1 in your car, Castrol won't be put in mine. The same thing would go with other off-brand ones because they are harder to get and if for some reason the specification ins't on the bottle (even though it's a better oil), the manufacturer WILL GET in a pissing match should something happen. While I can't speak for carbon buildup (even on my B7 A4), I will say that I've always used M1 in all my cars and they've all survived until 100k+ miles with no issues. It just seems to work and it sure is easier to find than the Redline oils I used to use years ago.

[Moose201]

AndyUK, this is the M1 that most of us are using:

http://www.mobiloil.com/USA-English/..._1_0W-40.aspx#

At the bottom of the web page there are links to the Product Data Sheet as well as the MSDS. Many of us buy this oil at Wal-Mart where a 5 quart jug costs about $27.

[AndyUK]

Its swings and roundabouts. 504/507 is a “fuel economy” oil that is also supposed to control deposit build-up better mid-full SAPS oils by keeping insolubles lower. This should keep deposits lower. HOWEVER, this is not our experience. Its cleaning power is limited so the engine burns more oil if there are deposits on the pistons/rings, resulting in more oil recirculating through the system. Mid-full SAPS oils clean much better and there is good evidence that oil consumption is reduced. They need to be changed more frequently though.

Take any brand and check their flagship oil. The most expensive, highest performance lube and you will struggle to find a 504/507 approval.

I am speaking generally now and not specifically about the 504/507 – some oil specifications offer value to the quality of the lubricant whereas others actually restrict oil quality/performance. This means that some oils are inferior by design.

FWIW, I did a little checking and it appears the low-SAPS oil was developed to protect diesel particulate filters AND modern catalytic converters.

eg http://www.oelcheck.de/en/knowledge-...ring-2010.html

It would appear that "Phosphorus and sulphur are highly poisonous to catalytic converters".

I'm no expert but that phrase came up fairly often in internet searches.

Maybe it's more of a question of degrees vs black/white re using low SAPS or not in a gasoline engine or perhaps there are differences in catalytic converter materials so this doesn't apply to all of them.

[BoostEasy]

Its swings and roundabouts. 504/507 is a “fuel economy” oil that is also supposed to control deposit build-up better mid-full SAPS oils by keeping insolubles lower. This should keep deposits lower. HOWEVER, this is not our experience. Its cleaning power is limited so the engine burns more oil if there are deposits on the pistons/rings, resulting in more oil recirculating through the system. Mid-full SAPS oils clean much better and there is good evidence that oil consumption is reduced. They need to be changed more frequently though.

Take any brand and check their flagship oil. The most expensive, highest performance lube and you will struggle to find a 504/507 approval.

I am speaking generally now and not specifically about the 504/507 – some oil specifications offer value to the quality of the lubricant whereas others actually restrict oil quality/performance. This means that some oils are inferior by design.

Thanks for the reply Andy but I'm not sure if this answered my question. I understand that the higher SAPS tends to protect the engine better vs low SAPS, but is it likely the mid/higher SAPS oil will shorten the effective life of the catalytic converter or reduce it's performance enough to fail an emission test (eg CA) after say 80k miles in a modern car like a B8 S4 3.0T? If it's not going to materially affect the catalytic converter I'm leaning towards a mid/high SAPS oil for the first oil change (5k) on my 2014 S5.

[AndyUK]

Apologies the first part of my response didn't get posted so I must have screwed up somewhere.


The missing part….

It is not that simple. Sulphated ash is much more damaging to DPFs than CATs plus NOT ALL ash is actually harmful. If it was then all the branded 502/505 spec oils wouldn’t actually meet the spec. There are limits to certain ingredients in order to meet the spec. With 504/507 there are very low limits but this is to protect the DPF because the ash is not easily combusted as part of the regeneration process.

If concerned then a mid-SAPs is always an option.

Thanks for the reply Andy but I'm not sure if this answered my question. I understand that the higher SAPS tends to protect the engine better vs low SAPS, but is it likely the mid/higher SAPS oil will shorten the effective life of the catalytic converter or reduce it's performance enough to fail an emission test (eg CA) after say 80k miles in a modern car like a B8 S4 3.0T? If it's not going to materially affect the catalytic converter I'm leaning towards a mid/high SAPS oil for the first oil change (5k) on my 2014 S5.

[mr shickadance]

Andy, still looking for a recommendation for off the shelf oil that you would run in your car?

[shadycrew31]

I've been sitting back enjoying this discussion.

Here is what I use.

http://www.mobiloil.com/USA-English/..._1_0W-40.aspx#

[RecklessactN]

I had my car in for A/C pressure switch issue, to be replaced under warranty. Not my usual service rep called me back and said I was throwing the code related to the carbon build up, but they will not cover under warranty because I am tuned. I said ,"so even though I am tuned and this being a known issue, I can't get the service?" She said pretty much, but I intend to press my case in person when I return with the service manager. I saw one other post in here with a success story, but has anyone else get told "no" flat out?

[visualguy]

I agree but unfortunately I don't have all the answers - wish I did. I'm not aware of any significant difference in valve materials across the Audi DI range.

We were hoping to establish more common denominators with regards to the speed and degree of build-up but with the many variables involved this takes time and money.

Right, but then we're basically back to square one - that is, we don't really know enough about how and why this buildup happens, or at least we don't know some key contributing factors. Sure, carbon bonds to the valve material and then to the carbon that already formed there, but this is a trivial observation - it just re-states the observed problem.

There seem to be ways to decrease the severity of this problem significantly without adding port injection (and without forced induction). I think if we understood what Audi does differently in the 4.2 FSI in the RS5, or what Porsche does differently in the A91 engine, we would have a better understanding of the root causes of this problem. If the difference is not in valve materials, then, like I said, we're back to square one in terms of our understanding of this. Oil is going to get on the valve stems in all these engines and it won't be cleaned by fuel, right? So, what's the difference?

[audistealth]

I had my car in for A/C pressure switch issue, to be replaced under warranty. Not my usual service rep called me back and said I was throwing the code related to the carbon build up, but they will not cover under warranty because I am tuned. I said ,"so even though I am tuned and this being a known issue, I can't get the service?" She said pretty much, but I intend to press my case in person when I return with the service manager. I saw one other post in here with a success story, but has anyone else get told "no" flat out?

There's a TSB for secondary air. That makes it a common issue recognized by Audi. Tell them they are full of shit and get back to work.

[RecklessactN]

There's a TSB for secondary air. That makes it a common issue recognized by Audi. Tell them they are full of shit and get back to work.

This made me laugh so hard, I forgot how mad I was. I get there and the rep tells me that my car didn't throw a code, it was just a notice that my vehicle had an extension... and then I was quoted for the work. You don't want to know the number...

[AndyUK]

If you don’t mind, what is the current mileage and what oil have you been using?

Did the dealer confirm if it was inlet valve carbon or somewhere else?

If you can get an oil sample we will pay for an oil analysis on our account with Blackstone.

I had my car in for A/C pressure switch issue, to be replaced under warranty. Not my usual service rep called me back and said I was throwing the code related to the carbon build up, but they will not cover under warranty because I am tuned. I said ,"so even though I am tuned and this being a known issue, I can't get the service?" She said pretty much, but I intend to press my case in person when I return with the service manager. I saw one other post in here with a success story, but has anyone else get told "no" flat out?

[AndyUK]

This is a full-SAPS oil in a low cost base. Contains some PAO and Esters but mainly group III. Looks about right for the price.

It is not a bad oil and meets 502/505.01.

Would I use it in my S4? No.

I've been sitting back enjoying this discussion.

Here is what I use.

http://www.mobiloil.com/USA-English/..._1_0W-40.aspx#

[AndyUK]

I am still mulling it over as I would never use an off-the-shelf oil on it own.

Andy, still looking for a recommendation for off the shelf oil that you would run in your car?

[AndyUK]

I am confused to how you have reached the conclusion that “we are back to square one?” I’m not sure if you have misunderstood the main facets of the research findings or if there are other reasons. The ROOT CAUSE of the problem has been established.

FACT 1: The majority of the build-up is oil from the valve stem lubrication process. This is the first common denominator and has been known for some time.

FACT 2: The oil is catalysing with the valve because of the nickel and chrome alloys used to harden the valve. This is the second common denominator and the ROOT CAUSE unforeseen by the manufacturer.

FACT 3: Due to a number of factors that I can’t detail now, the carbon remains chemically active to such a degree that it becomes a “magnet” for ALL CARBON SPECIES.
This provides us with very valuable information such as WHY the oil bonds so readily (FACT 2) and WHY it won’t self-manage (FACT 3). Are there other factors? Of course, but the fact remains that all TFSI engines suffer from build-up. We also know that NA engines are worse off etc., etc. The main variable is mileage.

If you have other data that negates this then I would be grateful to see it. There are some very clever minds working on this and I’m sure they are already aware of what other DI manufactures (i.e. Porsche), are doing. As one of the team is a Metallurgy Professor, I would certainly hope so. Moreover, I am not privy to all the information and some of the information that I am privy to I cannot publicise. If your response was based on a frustration that I was unable to answer all the questions then I apologise but please understand you are one of the first public to hear about this and it’s free, including my time to explain it.

The RS5 is also struggling. I’m sure that Audi have tried to mitigate the issue over the last few years with different valve seal materials, maybe a different hardening process with less active metals (knowingly or unkowingly), or similar design features that would explain differences between models etc. etc. etc. However, with this recent breakthrough I suspect attention will be focused on ways to eliminate the catalytic reaction and chemical activity rather than trying the wrestle with the huge array of variables as to why x TSFI engine has accumulated 25% more deposits that y TFSI engine.

Right, but then we're basically back to square one - that is, we don't really know enough about how and why this buildup happens, or at least we don't know some key contributing factors. Sure, carbon bonds to the valve material and then to the carbon that already formed there, but this is a trivial observation - it just re-states the observed problem.

There seem to be ways to decrease the severity of this problem significantly without adding port injection (and without forced induction). I think if we understood what Audi does differently in the 4.2 FSI in the RS5, or what Porsche does differently in the A91 engine, we would have a better understanding of the root causes of this problem. If the difference is not in valve materials, then, like I said, we're back to square one in terms of our understanding of this. Oil is going to get on the valve stems in all these engines and it won't be cleaned by fuel, right? So, what's the difference?