Acceptably Safe Soot Levels: Can Anyone Speak with Authority? - Page 2 - PeachParts Mercedes-Benz Forum

shertex · #16 12-17-2010, 06:37 PM

Quote:

Originally Posted by Craig

Is he saying that he can detect an increased amount of bearing wear at higher soot levels?

I think so. Although he's mistaken about a higher lead level; it was only iron that was higher on the second sample. So I think I can conclude there's no evidence of increased bearing wear.

jonbobshinigin · #17 12-17-2010, 07:10 PM

I was just about to make a post JUST like this. Fortunately you did a much better job at articulating! Thanks, I will be keeping an eye on this one!

My purpose for asking is as another person mentioned; despite the brand/type of oil, it seems that the soot level is the same and that at a certain amount of miles the amount of soot suspended in the oil justifies changing the oil. I am wanting some conclusive evidence on this!

Pierre Hadary, who changes his old every 3k I believe, says his oil is somewhat clear after an oil change and a drive around the block. He is weary about my 7-8k interval using Mobil 1 TDT Synthetic 5w40.

I know this has been mentioned, but I figure I'd add my two cents.

shertex · #18 12-17-2010, 07:25 PM

I must admit, my working assumption over the last several years has been that suspended soot can do no harm. Now I'm thinking that's probably incorrect.

I hate to keep referring to Marshall Booth....but he knew these cars as well as anyone (at least that's my impression) and he was a strong proponent of long drain intervals and committed to long engine life. I can't imagine that if he thought, say, a 1.8% soot level could do any harm AT ALL that he would have recommended the longer intervals. And I'm sure it was perfectly obvious to him as it is to the rest of us the the LEVEL of soot production is not in any way dependent upon the oil used.

Back in 2003, when I got my first diesel, Dr. Booth was kind enough to email me on several occasions to "show me the ropes."

babymog · #19 12-17-2010, 07:27 PM

So the tech who did the oil analysis concludes that in his opinion, since extra miles shows additional soot and additional iron,1% should be the soot limit? Did he expect the additional miles to yield no more iron? Was the increase linear? This is not only a statistically insignificant sample but also a completely un-scientific conclusion. Furthermore, should you then try a 1000mile interval to see if it further decreases soot and/or iron levels? Seems like a witch-hunt mentality.

shertex · #20 12-17-2010, 07:33 PM

Quote:

Originally Posted by babymog

So the tech who did the oil analysis concludes that in his opinion, since extra miles shows additional soot and additional iron,1% should be the soot limit? Did he expect the additional miles to yield no more iron? Was the increase linear? This is not only a statistically insignificant sample but also a completely un-scientific conclusion. Furthermore, should you then try a 1000mile interval to see if it further decreases soot and/or iron levels? Seems like a witch-hunt mentality.

That's part of my perplexity. If ANY amount of soot harms the engine, then where does the logic end? Might as well go to 1000 mile intervals, if you have the time and patience.

But it's VERY difficult for me to believe that there's any sort of linear relationship between soot level and wear/engine life. Personally, I'd be happy to ride that curve many miles out until the slope made a marked turn upward.

babymog · #21 12-17-2010, 08:01 PM

Sorry, had to switch from my phone to the laptop to finish my thoughts.

Agreed, there must be a soot loading limit, and data on which it is based.

As others have stated, does max. soot loading change based on the oil? Oils, their additive packages, and the standards/classifications/ratings have changed. Does this mean that if M-B limited you to 2% in '87 with an oil that met minimum standards at that time, current premium synthetics could produce the same wear or less at 4%? Might be, hopefully someone here knows.

For the oil-analysis tech's opinion to be worth anything (IMO), I'd have to know: his credentials, the M-B Engineers' soot-loading limit, and the data on which it was calculated. Further, the data (5000miles vs 7500miles) would have to be from the same oil (not one sample at 5000, changed, new sample at 7500miles), and the driving conditions controlled/constant/documented. As mentioned above, much can change from one oil change to the next, even the change from summer to winter fuel, and from starts at ambient 70F to ambient 30F. Both of these changes will increase soot loading.

It is hard to determine the mileage for oil changes based on such a small amount of data. For those of us who run extended OCIs, the sample comes from the oil in the car, which is NOT changed unless the analysis indicates it should be. If not changed, the oil is run further and sampled/analyzed again. After several of these a trend will develop and it will predict oil change intervals and other service intervals.

To jump in the wayback machine, ... in '75 a certain airline was looking to reduce equipment downtime on its turbine aircraft. The oil analyses were documented along with physical engine teardowns, correlations and anomolies noted, everything calculated ad-naseum and presented to the FAA. Eventually they were able to extend some of the tear-downs based on oil analysis, which gave birth to the current method of predictive maintenance in turbine aircraft.

About the same time, we were curious about syn-oils in cars. Mobil 1 had recently been re-formulated to be compatible with regular oil, Amsoil had not yet. A couple of guys decided to buy new cars (one being my father) and compare different oils with oil analysis data from their 300mile commutes in their new cars, since the lab was available. Pretty cool stuff that. Big difference in wear metals between dino oils and synthetic oils, my Father and my family never buying a quart of dino oil in the 35years since.

A local trucking company (one of my clients at the time) switched to Delvac 1 when it became available (IIRC '78 or '79?) and started to run their 2-stroke DD semi trucks on it, using oil analysis to predict engine wear and maintenance, and never changed the oil until the first "in-frame" at 500,000miiles. They used a high-end bypass filtration system and simply added oil (a 2-stroke DD consumes/drips some oil so it did get renewed oil at a slow rate) based on the favorable oil analysis results. Further, the method increased fuel mileage, and decreased equipment downtime (scheduled and un-scheduled downtime = maintenance and failures).

So I believe in extended OCIs if the oil analysis supports it, and I believe in syn oils. To each their own. The extended OCI on syn oils reduces your pollution if you are dumping less oil, justifies the additional oil cost, and in my experience reduces oil consumption and fuel consumption which is all good. It isn't as easy as the dump and change at 5000 method, but some of us like to tinker and measure.

To the OP: I don't see anyone coming forward with the answer to the original post. I don't know where 2% comes from, nor 1%, and whether it still is valid based on new oil technology. I doubt very much that anyone will be able to answer the second half of that, but hope that at least someone will find out what the original soot-loading limit is and post a reference to the source. If it's 2%, I see no reason to change at 1.1%.

Kind of funny (to me anyway), back in the NMSL days there were those who claimed that 55mph should never be repealed because it saved fuel and was safer than higher speed limits. No doubt that that was true. However, there was another camp that claimed the 55mph NMSL saved as much fuel and lives as keeping everyone's tires properly inflated, and therefore we should replace the 55mph speed limit with curb-side cops armed with tire pressure gauges (this was long before the Explorer/Firestone/Tire-Pressure debacle).
The other part of that was that of course it was safer and more economical to drive slower, but where do we draw the line? You would be safer at 10mph than 55, so shouldn't we all drive 10mph then? You could fall over walking, shouln't we all crawl from place to place to avoid the tragic danger of falling over? In the end, it is all somewhat ambiguous to say that a certain soot loading is the max unless you have a target for how long you expect the engine to last internally, and under what conditions. The earlier rant about carrying a drum of fresh oil in the trunk to avoid any soot loading reiterated. Will the engine only last 400,000miles with 3% soot loading and average driving? I might be okay with that.

ah-kay · #22 12-17-2010, 08:07 PM

Quote:

Originally Posted by shertex

But it's VERY difficult for me to believe that there's any sort of linear relationship between soot level and wear/engine life. Personally, I'd be happy to ride that curve many miles out until the slope made a marked turn upward.

This seems to be a PhD research subject.

I would just change my oil at 3K mile or thereabout. Any oil better than no oil, dino or synthetic.

123Guy · #23 12-17-2010, 08:19 PM

We bought our 82 and 84 diesels since and have all the books, records, window stickers, etc.
Back then, MB said change the oil and filter every 3000 miles and adjust the valves every 12K. Nothing about the cars has changed, so I have kept on that schedule all these years. Both engines are tight as a drum.

layback40 · #24 12-17-2010, 08:37 PM

Quote:

Originally Posted by shertex

FWIW, here's a note from someone who works at the lab that did my oil analysis, explaning why he would stick to a 1% limit if he were in my shoes:

I would shoot for less than 1% on an automotive engine as the sump capacity is smaller and the potential damage with high soot. If you look at the sample we have been discussing you can notice a common pattern. Your previous sample had a low value of soot and the lead and iron values were much less than this sample of lead and iron. Lead is always from the rod and main bearings and generally lead/tin/copper are the bearing layers. The iron can be several places but it typically will elevate with soot. You are being very proactive with your vehicle maintenance and I just try to help with any advice i can provide with a "fellow gearhead". I would keep with the Delvac 1 as this is my product of choice with all my vehicles, gas and diesel. Keep the soot to less than 1%, (which could be excess idling, lots of local driving, or intake restriction), keep up with Delvac 1 and continue sampling and I see no reason why you can't get 400k plus.

This guy has answered your questions. I cant help but think that you dont like his answer & so are looking for justification to push the boundaries.

With regards to the late Marshal Booth ;
While not wishing to speak ill of the man, it is important to realize that he had no professional training in mechanical engineering or lubrication science. He was a smart man who specialized in pharmacology. his views on oil drain intervals etc had no scientific basis and have been shown to be floored.

While I personally do not claim to have specialty in lube oil chemistry, nor detailed analytical data for exactly your motor, I have previously taken regular advice from Caterpillar's engineering staff concerning the motors that power equipment I own. We are talking $500k+. The cost of a head rebuild would be greater than the replacement cost of your car. I change oil at their advice. The equipment is not stop start like a car, so soot is slower to build up. Their comments are in direct line with what you have been told by your oil tester.

I would not take too seriously advice from CAT or your oil tester about suitable medication for illnesses, I cant understand why some one would take advice from a pharmacist about oil/ lubrication/ motor ware.

Unfortunately in this day & age people are too quick to place trust in the opinion of people who are popular. Thats why advertisers use film stars for product endorsements. Their knowledge of the product is at best limited but too many believe they know best because of the false image they project.

shertex · #25 12-17-2010, 08:42 PM

Quote:

Originally Posted by layback40

This guy has answered your questions. I cant help but think that you dont like his answer & so are looking for justification to push the boundaries.

With regards to the late Marshal Booth ;
While not wishing to speak ill of the man, it is important to realize that he had no professional training in mechanical engineering or lubrication science. He was a smart man who specialized in pharmacology. his views on oil drain intervals etc had no scientific basis and have been shown to be floored.

Just looking for clarity one way or the other....trying to sort out people's honestly-held differences of opinions. Probably doesn't help to speculate on one another's motives....

Not familiar with that use of the word "floored." Perhaps an Aussie-ism? What does it mean?

shertex · #26 12-17-2010, 08:50 PM

Quote:

Originally Posted by layback40

This guy has answered your questions. I cant help but think that you dont like his answer & so are looking for justification to push the boundaries.

With regards to the late Marshal Booth ;
While not wishing to speak ill of the man, it is important to realize that he had no professional training in mechanical engineering or lubrication science. He was a smart man who specialized in pharmacology. his views on oil drain intervals etc had no scientific basis and have been shown to be floored.

While I personally do not claim to have specialty in lube oil chemistry, nor detailed analytical data for exactly your motor, I have previously taken regular advice from Caterpillar's engineering staff concerning the motors that power equipment I own. We are talking $500k+. I change oil at their advice. The equipment is not stop start like a car, so soot is slower to build up. Their comments are in direct line with what you have been told by your oil tester.
I would not take too seriously advice from CAT or your oil tester about suitable medication for illnesses, I cant understand why some one would take advice from a pharmasist about oil/ lubrication/ motor ware.

A lot of this begs the question....let's say you and I toss out the opinions of any and all without formal training in mechanical engineering, lubrication science, etc. (which of course would dipense with the vast majority of us on this forum). That STILL leaves real differences of opinion. Perhaps my recollection fails, but I'm fairly confident that MERCEDES uses a 2% soot limit. If that's the case, then why should I abide by the expert advice that urges me to stick to 1%?

layback40 · #27 12-17-2010, 08:55 PM

Quote:

Originally Posted by shertex

Not familiar with that use of the word "floored." Perhaps an Aussie-ism? What does it mean?

I means that it contains faults. Floored is faulty.
A crack in a casting is called a floor.
It is the floors in a diamond that cause the interesting appearance.

47dodge · #28 12-17-2010, 09:06 PM

I have seen 1% as the recommended max, from Oil Analyzers, the company I send my samples to. So far I have been staying within this advice.

A bypass filter goes a long way to keeping soot loading down. So would really recommend one if you want to go longer on the oil change intervals.

babymog · #29 12-17-2010, 09:06 PM

Layback:

I disagree. The question of what M-B considers the limit has not been answered, and the later question of why this tech considers 1% the limit for this engine has not been answered. Further, the tech notes higher soot, higher iron, and (apparently in error) higher lead in the higher mileage sample, which makes sense since it has 50% more miles' use. If this were subsequent miles and a statistically significant sample, I would then be interested in another critical piece of data: whether the increase is linear (whether the 50% greater mileage yielded any significant amount more than 50% greater wear metals).

Still further, the samples are from two separate fills, not two consecutive samples from the same oil which negates the value of any comparison, and of any conclusions derived from this comparison.

I still would like to read what the original Mercedes soot loading limit was (part of the original post/question).

layback40 · #30 12-17-2010, 09:47 PM

Quote:

Originally Posted by shertex

A lot of this begs the question....let's say you and I toss out the opinions of any and all without formal training in mechanical engineering, lubrication science, etc. (which of course would dipense with the vast majority of us on this forum). That STILL leaves real differences of opinion. Perhaps my recollection fails, but I'm fairly confident that MERCEDES uses a 2% soot limit. If that's the case, then why should I abide by the expert advice that urges me to stick to 1%?

I am surprised that no one has jumped in with the origin of this "spec". After your other thread yesterday, I spoke with my contact at CAT, His view was that if I was happy to do a motor rebuild at 8~10,000 hrs, then go for the higher soot limit. I am aiming for 20,000hrs on the motors without a rebuild.
The higher levels of lead in your oil at higher soot levels shows higher bearing ware rates. The bulk of the white metal forms a "mud" in the bottom of the sump as it settles.