OVERKILL
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Here are the pictures I mentioned that spurred this whole thread, as the guy has allowed me to post them:
Varnish: Is it really harmless?
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I have never seen varnish on a moving part [contact surfaces].
It is on the external surfaces of many others, though.
So until there is actual build up enough to be sludge, I see no harm in light to medium varnish.
Well... maybe heat retention is a possibility.
It is on the external surfaces of many others, though.
So until there is actual build up enough to be sludge, I see no harm in light to medium varnish.
Well... maybe heat retention is a possibility.
Originally Posted By: OVERKILL
But that's just it. Many (most?) of the cars will never have this problem. But the ones that DO have the problem, appear to suffer from varnish build-up and I'm curious as to the correlation. This is a huge double roller chain that spans both banks too, so slap and whip may be of far greater detriment in this application than in others.
Do the Modulars use double row timing chains? Something from my memory tells me they are single row. If that is correct, that may play a part here, too. A double row chain would have more inertia and more mass for a tensioner to control; there may be some unique requirements of a tensioner in this situation compared with others. Even this last set of pictures doesn't look that bad to me; about typical for an engine using long OCIs. If the various components are too sensitive to this type of deposit formation, then perhaps the oil change interval is too long as specified. It certainly wouldn't be the first time that's happened in the history of the automobile.
But that's just it. Many (most?) of the cars will never have this problem. But the ones that DO have the problem, appear to suffer from varnish build-up and I'm curious as to the correlation. This is a huge double roller chain that spans both banks too, so slap and whip may be of far greater detriment in this application than in others.
Do the Modulars use double row timing chains? Something from my memory tells me they are single row. If that is correct, that may play a part here, too. A double row chain would have more inertia and more mass for a tensioner to control; there may be some unique requirements of a tensioner in this situation compared with others. Even this last set of pictures doesn't look that bad to me; about typical for an engine using long OCIs. If the various components are too sensitive to this type of deposit formation, then perhaps the oil change interval is too long as specified. It certainly wouldn't be the first time that's happened in the history of the automobile.
Originally Posted By: OVERKILL
Originally Posted By: mechanicx
Originally Posted By: Hokiefyd
I may be in the minority opinion here, but I'd say that the level of varnish depicted above is not causing timing chain tensioner failures. Or if it is, then the BMW tensioners are much more sensitive to varnish than most. Those engines look very clean to me.
I think so too. Lots or all engines have varying degrees of varnish, but they don't all have early valvetrain failures. Overkill is probably just trying cover for BMW fragility with varnish
.
But that's just it. Many (most?) of the cars will never have this problem. But the ones that DO have the problem, appear to suffer from varnish build-up and I'm curious as to the correlation. This is a huge double roller chain that spans both banks too, so slap and whip may be of far greater detriment in this application than in others.
And that's precisely the issue: correlation.
Correlation is not causality. All those cars had gasoline in their tanks...so, clearly the ones that failed were using gasoline...but it's not safe to say that gasoline caused the timing chain failure...
I've seen engines run over 200K with worse varnish (not sludge, just a slight buildup on non-moving parts)...so varnish, per se, is not causing the chain problem...
Is it related? Could the varnish and the failure have the same root cause? Ah, that's an interesting question...
Originally Posted By: mechanicx
Originally Posted By: Hokiefyd
I may be in the minority opinion here, but I'd say that the level of varnish depicted above is not causing timing chain tensioner failures. Or if it is, then the BMW tensioners are much more sensitive to varnish than most. Those engines look very clean to me.
I think so too. Lots or all engines have varying degrees of varnish, but they don't all have early valvetrain failures. Overkill is probably just trying cover for BMW fragility with varnish
But that's just it. Many (most?) of the cars will never have this problem. But the ones that DO have the problem, appear to suffer from varnish build-up and I'm curious as to the correlation. This is a huge double roller chain that spans both banks too, so slap and whip may be of far greater detriment in this application than in others.
And that's precisely the issue: correlation.
Correlation is not causality. All those cars had gasoline in their tanks...so, clearly the ones that failed were using gasoline...but it's not safe to say that gasoline caused the timing chain failure...
I've seen engines run over 200K with worse varnish (not sludge, just a slight buildup on non-moving parts)...so varnish, per se, is not causing the chain problem...
Is it related? Could the varnish and the failure have the same root cause? Ah, that's an interesting question...
Yeah also the ones without varnish probably had more frequent oil changes and maybe better quality oil used. But we still don't have causation. It looks like there were chain failures with even low to average varnish. I think it's probably mostly the valvetrain design to blame. It's possible failures are higher when operated in conditions that lead to more varnish, but I don't think the cause is the varnish.
What they are calling a "guide" is really more of an idler as its changing the path slightly of the chain. Its not just holding it in place from slipping off.
OVERKILL
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Originally Posted By: Hokiefyd
Do the Modulars use double row timing chains? Something from my memory tells me they are single row.
They are single row as far as I know.
Quote:
If that is correct, that may play a part here, too. A double row chain would have more inertia and more mass for a tensioner to control; there may be some unique requirements of a tensioner in this situation compared with others.
Well, that's the interesting part. A couple of the M62's posted are single roller. The early M62 was double-roller like the S62. The S62 was always double-roller. Apparently the double-roller M62 didn't have the issue???
Quote:
Even this last set of pictures doesn't look that bad to me; about typical for an engine using long OCIs. If the various components are too sensitive to this type of deposit formation, then perhaps the oil change interval is too long as specified. It certainly wouldn't be the first time that's happened in the history of the automobile.
The guy owning that engine, he put it in with 120,000Km on it (75,000 miles) and his change interval was 5,000Km!!! Definitely not extended drains happening. That was about 8 years ago (when that engine was put in the car, the original had rod knock). So 8 years on 5,000Km (3,000 mile) OCI's didn't seem to do much for the varnish....
Do the Modulars use double row timing chains? Something from my memory tells me they are single row.
They are single row as far as I know.
Quote:
If that is correct, that may play a part here, too. A double row chain would have more inertia and more mass for a tensioner to control; there may be some unique requirements of a tensioner in this situation compared with others.
Well, that's the interesting part. A couple of the M62's posted are single roller. The early M62 was double-roller like the S62. The S62 was always double-roller. Apparently the double-roller M62 didn't have the issue???
Quote:
Even this last set of pictures doesn't look that bad to me; about typical for an engine using long OCIs. If the various components are too sensitive to this type of deposit formation, then perhaps the oil change interval is too long as specified. It certainly wouldn't be the first time that's happened in the history of the automobile.
The guy owning that engine, he put it in with 120,000Km on it (75,000 miles) and his change interval was 5,000Km!!! Definitely not extended drains happening. That was about 8 years ago (when that engine was put in the car, the original had rod knock). So 8 years on 5,000Km (3,000 mile) OCI's didn't seem to do much for the varnish....
OVERKILL
$100 Site Donor 2021
Originally Posted By: Astro14
And that's precisely the issue: correlation.
Correlation is not causality. All those cars had gasoline in their tanks...so, clearly the ones that failed were using gasoline...but it's not safe to say that gasoline caused the timing chain failure...
I've seen engines run over 200K with worse varnish (not sludge, just a slight buildup on non-moving parts)...so varnish, per se, is not causing the chain problem...
Is it related? Could the varnish and the failure have the same root cause? Ah, that's an interesting question...
My theory here revolves around the sticky nature of varnish in conjunction with the weight of this timing chain setup. Tension is of course achieved, maintained and regulated through little hydraulic cylinders. If their ability to properly regulate the chain tension is compromised through poor lubricant flow, sticking....etc, then the chain will have a tendency to flap/slap/whip and potentially destroy the guides/tensioners, which are, after all, plastic.
And that's precisely the issue: correlation.
Correlation is not causality. All those cars had gasoline in their tanks...so, clearly the ones that failed were using gasoline...but it's not safe to say that gasoline caused the timing chain failure...
I've seen engines run over 200K with worse varnish (not sludge, just a slight buildup on non-moving parts)...so varnish, per se, is not causing the chain problem...
Is it related? Could the varnish and the failure have the same root cause? Ah, that's an interesting question...
My theory here revolves around the sticky nature of varnish in conjunction with the weight of this timing chain setup. Tension is of course achieved, maintained and regulated through little hydraulic cylinders. If their ability to properly regulate the chain tension is compromised through poor lubricant flow, sticking....etc, then the chain will have a tendency to flap/slap/whip and potentially destroy the guides/tensioners, which are, after all, plastic.
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Out of curiosity, (I have no BMW in this horse race), do BMW's (or certain BMW engines) have a propensity for varnish/sludge or are they simply not maintained as much as other cars under the presumption they are better engineered than others (not saying that all BMW owners are doing this)? Obviously, all engines could varnish/sludge if not maintained, but I have seen quite a few BMWs with varnish/sludge issues in forums and on the Internet. Is this because the OCIs are too long?
The design/routing of the timing chains seems to be begging for something to go wrong (especially if the wear "plates" go), but then again, if hydraulic "followers" are being used, then oil selection and maintenance becomes more of an issue ans so I tend to agree that varnish would affect those followers.
The design/routing of the timing chains seems to be begging for something to go wrong (especially if the wear "plates" go), but then again, if hydraulic "followers" are being used, then oil selection and maintenance becomes more of an issue ans so I tend to agree that varnish would affect those followers.
I'm having a hard time believing that the engine in the last set of pictures saw exclusively 3k mile ocis. This is internet after all and all sorts of things are posted just to mess with everybody.
OVERKILL
$100 Site Donor 2021
Originally Posted By: KrisZ
I'm having a hard time believing that the engine in the last set of pictures saw exclusively 3k mile ocis. This is internet after all and all sorts of things are posted just to mess with everybody.
Note that I said that it had 5K/3K (Km/miles) OCI's after he put it in. The engine had 75,000 miles on it when he bought it.
It was probably dealer maintained before that, so it would (should?) have got BMW/Castrol 5w-30 @ OLM intervals, which can be extremely long.
I'm having a hard time believing that the engine in the last set of pictures saw exclusively 3k mile ocis. This is internet after all and all sorts of things are posted just to mess with everybody.
Note that I said that it had 5K/3K (Km/miles) OCI's after he put it in. The engine had 75,000 miles on it when he bought it.
It was probably dealer maintained before that, so it would (should?) have got BMW/Castrol 5w-30 @ OLM intervals, which can be extremely long.
OVERKILL
$100 Site Donor 2021
Originally Posted By: 2010_FX4
Out of curiosity, (I have no BMW in this horse race), do BMW's (or certain BMW engines) have a propensity for varnish/sludge or are they simply not maintained as much as other cars under the presumption they are better engineered than others (not saying that all BMW owners are doing this)? Obviously, all engines could varnish/sludge if not maintained, but I have seen quite a few BMWs with varnish/sludge issues in forums and on the Internet. Is this because the OCIs are too long?
The design/routing of the timing chains seems to be begging for something to go wrong (especially if the wear "plates" go), but then again, if hydraulic "followers" are being used, then oil selection and maintenance becomes more of an issue ans so I tend to agree that varnish would affect those followers.
With respect to them having a propensity to develop varnish/sludge? Well, it appears they may on the OEM lubricants
They do have OLM's that run the oil for rather significant distances. The OEM lubricant (in these applications) is either BMW/Castrol 5w-30, which is a group 3 synthetic with an HTHS >=3.5cP, or, with the S62, Castrol TWS 10w-60.
I don't have a great deal of faith in the OLM after mine didn't appear to compensate AT ALL for the massive fuel dilution I was experiencing with my short tripping this winter. Had I been your regular Joe, I'd still be running that fill
Though maybe it got better in later years, as my sister's '03 330i has actually asked her to change the oil recently. She had last done it in the fall when it was done at the dealership when they replaced her filter housing
This reinforces the importance of leveraging UOA's for tracking lubricant health outside of ideal operating conditions. Mine clearly illustrated to me that 10,000Km is too far doing mostly short trips in a Canadian winter, even on a premium synthetic (M1 0w-40).
Out of curiosity, (I have no BMW in this horse race), do BMW's (or certain BMW engines) have a propensity for varnish/sludge or are they simply not maintained as much as other cars under the presumption they are better engineered than others (not saying that all BMW owners are doing this)? Obviously, all engines could varnish/sludge if not maintained, but I have seen quite a few BMWs with varnish/sludge issues in forums and on the Internet. Is this because the OCIs are too long?
The design/routing of the timing chains seems to be begging for something to go wrong (especially if the wear "plates" go), but then again, if hydraulic "followers" are being used, then oil selection and maintenance becomes more of an issue ans so I tend to agree that varnish would affect those followers.
With respect to them having a propensity to develop varnish/sludge? Well, it appears they may on the OEM lubricants
They do have OLM's that run the oil for rather significant distances. The OEM lubricant (in these applications) is either BMW/Castrol 5w-30, which is a group 3 synthetic with an HTHS >=3.5cP, or, with the S62, Castrol TWS 10w-60.
I don't have a great deal of faith in the OLM after mine didn't appear to compensate AT ALL for the massive fuel dilution I was experiencing with my short tripping this winter. Had I been your regular Joe, I'd still be running that fill
This reinforces the importance of leveraging UOA's for tracking lubricant health outside of ideal operating conditions. Mine clearly illustrated to me that 10,000Km is too far doing mostly short trips in a Canadian winter, even on a premium synthetic (M1 0w-40).
Originally Posted By: OVERKILL
Originally Posted By: KrisZ
I'm having a hard time believing that the engine in the last set of pictures saw exclusively 3k mile ocis. This is internet after all and all sorts of things are posted just to mess with everybody.
The engine had 75,000 miles on it when he bought it.
It was probably dealer maintained before that, so it would (should?) have got BMW/Castrol 5w-30 @ OLM intervals, which can be extremely long.
That I imagine is the culprit. Don't some of those OLM go out to like 10K to 15K miles? So theoretically it's possible that the car only received 5 oil changes in it's lifetime before the current owner took over.
Originally Posted By: KrisZ
I'm having a hard time believing that the engine in the last set of pictures saw exclusively 3k mile ocis. This is internet after all and all sorts of things are posted just to mess with everybody.
The engine had 75,000 miles on it when he bought it.
It was probably dealer maintained before that, so it would (should?) have got BMW/Castrol 5w-30 @ OLM intervals, which can be extremely long.
That I imagine is the culprit. Don't some of those OLM go out to like 10K to 15K miles? So theoretically it's possible that the car only received 5 oil changes in it's lifetime before the current owner took over.
You want varnish? I'll show you varnish...Camry I4 @ 100k miles
The result of either
10k mi. OCI with recommended dino (despite Owner1's claim at 5k OCI), likely Shell oil as told to me by curly moe and larry who did the OCs....1 cup drop-off after 3k miles since I bought it @ 97k miles (prev. fill was PYB)
or
failing gunked up PCV valve...
in either case I'm going with PP 5w-30 and 5k mi. OCIs
The result of either
10k mi. OCI with recommended dino (despite Owner1's claim at 5k OCI), likely Shell oil as told to me by curly moe and larry who did the OCs....1 cup drop-off after 3k miles since I bought it @ 97k miles (prev. fill was PYB)
or
failing gunked up PCV valve...
in either case I'm going with PP 5w-30 and 5k mi. OCIs
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Varnish is never "harmless". the harm that it does is determined by where it ends up.
It's often formed in one part of the system, held in solution until it leaves that part, and then deposits out where flow rate drops (if in suspension), or when the oil cools (in solution). It's polar, so it like to cling to metal, and then once there, invite it's friends to hold hands too, and thicken/darken.
So "dead ends" in lubricating systems like actuators are often places for oil to cool and varnish to deposit.
Your actuator theory is fair, as I have seen first hand on a number of occasions apparent light varnish jam actuators mid stroke when cold, free up when hot...and in industry, there have been many millions of dollars of failed expensive equipment when control gear has stuck, and allowed equipment runaway.
I
It's often formed in one part of the system, held in solution until it leaves that part, and then deposits out where flow rate drops (if in suspension), or when the oil cools (in solution). It's polar, so it like to cling to metal, and then once there, invite it's friends to hold hands too, and thicken/darken.
So "dead ends" in lubricating systems like actuators are often places for oil to cool and varnish to deposit.
Your actuator theory is fair, as I have seen first hand on a number of occasions apparent light varnish jam actuators mid stroke when cold, free up when hot...and in industry, there have been many millions of dollars of failed expensive equipment when control gear has stuck, and allowed equipment runaway.
I
OVERKILL
$100 Site Donor 2021
Originally Posted By: Shannow
Varnish is never "harmless". the harm that it does is determined by where it ends up.
It's often formed in one part of the system, held in solution until it leaves that part, and then deposits out where flow rate drops (if in suspension), or when the oil cools (in solution). It's polar, so it like to cling to metal, and then once there, invite it's friends to hold hands too, and thicken/darken.
So "dead ends" in lubricating systems like actuators are often places for oil to cool and varnish to deposit.
Your actuator theory is fair, as I have seen first hand on a number of occasions apparent light varnish jam actuators mid stroke when cold, free up when hot...and in industry, there have been many millions of dollars of failed expensive equipment when control gear has stuck, and allowed equipment runaway.
I
Thank you Shannow, I appreciate your input here
Varnish is never "harmless". the harm that it does is determined by where it ends up.
It's often formed in one part of the system, held in solution until it leaves that part, and then deposits out where flow rate drops (if in suspension), or when the oil cools (in solution). It's polar, so it like to cling to metal, and then once there, invite it's friends to hold hands too, and thicken/darken.
So "dead ends" in lubricating systems like actuators are often places for oil to cool and varnish to deposit.
Your actuator theory is fair, as I have seen first hand on a number of occasions apparent light varnish jam actuators mid stroke when cold, free up when hot...and in industry, there have been many millions of dollars of failed expensive equipment when control gear has stuck, and allowed equipment runaway.
I
Thank you Shannow, I appreciate your input here
So lots of conflicting information in this thread when compared to other OCI threads and pics. We read that maybe 10K dino intervals are likely culprits, that Castrol is to blame, some going to use PP on 5K intervals to clean up or prevent varnish...We have loads of advice from other threads saying most synth oils are good for 10K miles, OLM are fairly accurate with some cars but not others, OEM's concerned with getting through the warranty or are they pretty accurate. Should all Castrol oils be avoided like the plague?
Are Randomhero and/or TooSlicks OCI formulas to be believed even moderately even though they are fairly well regarded.
As far as I know, varnish doesn't show up in a used oil analysis, yet it is cause for concern? How does anyone know even with UOA that looks stellar what varnish lurks in the recesses of the engine? How much can one really know about varnish looking through the oil fill hole anyway?
What really matters and when newbs come on to this site are they getting confused by all the seemingly conflicting information?
Are Randomhero and/or TooSlicks OCI formulas to be believed even moderately even though they are fairly well regarded.
As far as I know, varnish doesn't show up in a used oil analysis, yet it is cause for concern? How does anyone know even with UOA that looks stellar what varnish lurks in the recesses of the engine? How much can one really know about varnish looking through the oil fill hole anyway?
What really matters and when newbs come on to this site are they getting confused by all the seemingly conflicting information?
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OVERKILL
$100 Site Donor 2021
Originally Posted By: Smokescreen
So lots of conflicting information in this thread when compared to other OCI threads and pics. We read that maybe 10K dino intervals are likely culprits, that Castrol is to blame, some going to use PP on 5K intervals to clean up or prevent varnish...We have loads of advice from other threads saying most synth oils are good for 10K miles, OLM are fairly accurate with some cars but not others, OEM's concerned with getting through the warranty or are they pretty accurate. Should all Castrol oils be avoided like the plague?
Are Randomhero and/or TooSlicks OCI formulas to be believed even moderately even though they are fairly well regarded.
As far as I know, varnish doesn't show up in a used oil analysis, yet it is cause for concern? How does anyone know even with UOA that looks stellar what varnish lurks in the recesses of the engine? How much can one really know about varnish looking through the oil fill hole anyway?
What really matters and when newbs come on to this site are they getting confused by all the seemingly conflicting information?
Smokescreen:
I have no easy answer to your questions. I don't think there is one. I will however add some points that may help to at least give us some focus:
1. Do we know what causes varnish? If so, then we should be able to determine what engines and what operating conditions are most likely to make it form.
2. Do we know what oils appear to be more likely to allow varnish to form? If so, does subsequently ceasing to recommend them for applications that fall under #1 above make sense?
3. There is no formula that will provide an ideal OCI for all engines under all operating conditions using any lubricant. There are too many variables within those spectra.
4. Whether varnish causes harm or is relatively benign is going to depend on where it is formed. This will vary from engine family to engine family, so there is no simple "varnish is harmless" or "varnish is the plague of black death". People like to use the first one because we see so much of it, that to dismiss it is a "feel good". I've never felt good about varnish because I know it has the potential to cause serious issues if it forms in the wrong place. Shannow has echoed my sentiment on this. You could say that varnish is only harmless until it isn't.
5. With respect to the fill-hole view. I've never had an engine apart that was clean there and filthy everywhere else. Take that for what its worth.
6. If newbs are getting confused, then they are no different than the rest of us
Simplifying it to black and white do's and do not's is unfair to everybody. The grey area is massive.
So lots of conflicting information in this thread when compared to other OCI threads and pics. We read that maybe 10K dino intervals are likely culprits, that Castrol is to blame, some going to use PP on 5K intervals to clean up or prevent varnish...We have loads of advice from other threads saying most synth oils are good for 10K miles, OLM are fairly accurate with some cars but not others, OEM's concerned with getting through the warranty or are they pretty accurate. Should all Castrol oils be avoided like the plague?
Are Randomhero and/or TooSlicks OCI formulas to be believed even moderately even though they are fairly well regarded.
As far as I know, varnish doesn't show up in a used oil analysis, yet it is cause for concern? How does anyone know even with UOA that looks stellar what varnish lurks in the recesses of the engine? How much can one really know about varnish looking through the oil fill hole anyway?
What really matters and when newbs come on to this site are they getting confused by all the seemingly conflicting information?
Smokescreen:
I have no easy answer to your questions. I don't think there is one. I will however add some points that may help to at least give us some focus:
1. Do we know what causes varnish? If so, then we should be able to determine what engines and what operating conditions are most likely to make it form.
2. Do we know what oils appear to be more likely to allow varnish to form? If so, does subsequently ceasing to recommend them for applications that fall under #1 above make sense?
3. There is no formula that will provide an ideal OCI for all engines under all operating conditions using any lubricant. There are too many variables within those spectra.
4. Whether varnish causes harm or is relatively benign is going to depend on where it is formed. This will vary from engine family to engine family, so there is no simple "varnish is harmless" or "varnish is the plague of black death". People like to use the first one because we see so much of it, that to dismiss it is a "feel good". I've never felt good about varnish because I know it has the potential to cause serious issues if it forms in the wrong place. Shannow has echoed my sentiment on this. You could say that varnish is only harmless until it isn't.
5. With respect to the fill-hole view. I've never had an engine apart that was clean there and filthy everywhere else. Take that for what its worth.
6. If newbs are getting confused, then they are no different than the rest of us
Originally Posted By: OVERKILL
6. If newbs are getting confused, then they are no different than the rest of us
Simplifying it to black and white do's and do not's is unfair to everybody. The grey area is massive.
Bang on statement. If we could simplify everything to Do's and Don'ts then this forum would've been dead long time ago.
What noobs need to do is spend more time reading and trying to understand that there is no "holy grail" or one size fits all type of answer, instead of recommending PU or 0w20 oils in every thread because that's the most popular topic at the time.
6. If newbs are getting confused, then they are no different than the rest of us
Bang on statement. If we could simplify everything to Do's and Don'ts then this forum would've been dead long time ago.
What noobs need to do is spend more time reading and trying to understand that there is no "holy grail" or one size fits all type of answer, instead of recommending PU or 0w20 oils in every thread because that's the most popular topic at the time.
agreed. that massive gray area has the answer. I can't simply correlate varnish to be the cause of failure. If one found a jammed tensioner that was perhaps jammed by varnish or otherwise starved by it, sure. But then you could also call that poor design---... tensioner not lubed correctly / sealed correctly / fed correctly / designed with proper clearances, etc.. easily cluttered by the unknown numbers of how many vehicles run all day long with varnish, doing just fine. when something breaks.... how do you know *that* was the cause?
BMWs can be weird machines. ever set cam timing on one? even non-vanos models? did you spring for the $260 alignment tool? I think they make some weird decisions in their engine designs and materials selection.
Furthermore, chain guides and tensioner designs have their dark moments across several brands-- so this is a potential hotbed area to use as a measure of engine health, oil health, etc..
I once complained to a manager in my chain of command about how something was going. he countered my complaint, sort of a devil's advocate direction. I think I told him to cut the "glass is half full" [stuff] and he got me good. he said that the glass was neither half full or half empty and that I was so junior for seeing only that, when, in truth, the glass was over-engineered to twice the needed capacity.
so tensioner... varnish... design?
BMWs can be weird machines. ever set cam timing on one? even non-vanos models? did you spring for the $260 alignment tool? I think they make some weird decisions in their engine designs and materials selection.
Furthermore, chain guides and tensioner designs have their dark moments across several brands-- so this is a potential hotbed area to use as a measure of engine health, oil health, etc..
I once complained to a manager in my chain of command about how something was going. he countered my complaint, sort of a devil's advocate direction. I think I told him to cut the "glass is half full" [stuff] and he got me good. he said that the glass was neither half full or half empty and that I was so junior for seeing only that, when, in truth, the glass was over-engineered to twice the needed capacity.
so tensioner... varnish... design?
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