Yeh, I was wondering if a bypass filter would remove soot. If so I am going to install one soon. My friend is an amsoil and bypass filter and goes 20k between changes. And his gmc truck has 300k+. let's talk about bypass filter setups please!

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1987 300TDT - 195,000 (Original #14 head)
1993 190E 2.3 - 105,000
1981 300D - 250,000

Nothing in the engine runs with no clearance, it all has clearance. The problem then would be not the quantity of the carbon/soot, but the size of the particles. Provided the full-flow portion of the filter is not clogged/bypassing then, and the filtration is smaller than the clearance between moving parts, I am still missing the mechanics of damage from soot loading. I'm not trying to be a smartass, just my Engineer side trying to understand a facet of engine wear or potential wear which has never been part of my expertise and I thank you all for sustaining this discussion.

__________________

Gone to the dark side

- Jeff

The challenge would be to identify the minimum clearance between any two parts that are exposed to engine oil. Do we know the minimum clearance between the rings and the cylinder walls or between the parts of the timing chain?

I looked at my detriot diesel service manuel and it says 1% max. So at least two sources I have found say 1%. detroits uses a luberfiner bypass filter for a lot of their engines. By the way this is all the old 2 cycle engines. I have not yet worked on the newer 4 cycle.

I have been using the Amsoil bypass for my 240, and my Dodge. Luberfiners on the larger engines.

Even if there is enough clearance for the dirt particles, they are not always suspended in the middle of the oil stream. Those at the edges are going to cause wear. Think like lapping compound. I know this is not the scientific answer you may be looking for, but hope it helps.

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1977 240D turbo

All this continues to be most interesting and informative. At the very least there's enough doubt cast on my original assumptions that I think I'm going to play it safe and go back to 5k or 6k drain intervals....that will certainly keep me below 1%. Mobil 1 at Walmart is cheap....plus I'm still mildly entertained by doing oil changes.

But I remain curious about the original questions.

Took a sample today from my 91 300D after 9500 miles....we'll see what the soot load looks like after analysis!

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 179k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 77k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Lapping compound can contain abrasives such as aluminum oxide, which are harder than the surfaces they're designed to abrade. If the soot is softer than the surface it contacts, the contacted surface does not get abraded. I selected many plastic fillers to change the properties of the plastics, talc / calcium carbonate is a common and cheap filler/extender, and is softer than aluminum so I used it, Kaolin, and others against an aluminum bearing surface successfully. If the soot is soft enough (thus my question about the Moh's hardness of soot particles) then it cannot damage the bearings, much like trying to scratch glass with teflon.

The hardness, if harder than the metals it contacts, would be a problem from the very start (think abrasive water-jet cutting) and no soot would be allowable, certainly not 1%. Further, if it is abrasive in an oil suspension, it certainly would be abrasive in air (now think sandblasting), and the damage to exhaust ports, cylinders, and especially in collision with the exhaust-gas turbine blades at high speeds would be substantial. I see none of this being a problem.

It is my expectation that the soot is not abrasive, and that it is a different machanism that makes it harmful. Possibly, if the structure is like Layback says, it is a matter of hooking/sticking together once there is enough of it in the oil to form large enough masses (agglomerate as Shertex put it) to block proper oil flow. or a similar problem leading to engine damage or increased wear.

Again following this assumption, different oil properties can cause it to stick together more or less often, so different oils would then be able to handle different soot loading depending on how they are formulated.

There are many possibilities, and my limited efforts so far have yielded no soot-loading limit from Mercedes, nor why it is bad. Until then we're just using the dunking stool to test for witches.

__________________

Gone to the dark side

- Jeff

For the really enterprising among us.... if you do a Google search for the words soot engine wear study a number of studies come up. You can read the abstracts but have to pay for the papers. My guess is the answers to our questions lie in papers like that.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 179k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 77k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

When a cam lobe pushes on a follower there is effectively no clearance apart from the oil film that is so thin that the surface Finnish of the surfaces comes into play. Thats why things ware, if there was always clearance, nothing would ever ware out.
The rings are under compression to make them fit in the bore. There is no clearance. If there was clearance there would be no friction & you could place a ring in a bore & it would fall out. That is why they use dissimilar metals to prevent most seizure.

Soot particles if formed under high temp & pressure are very hard & abrasive. The oil coats the particle & so minimizes the damage when it contacts motor parts. When the clearance is too small the oil is torn off the soot particle & the metal surfaces come into contact with the abrasive soot.

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Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

The oil film is by design always present. providing "clearance" between the rings and cylinder bore, between the tappets and cam lobes, between the cam and bearings, etc.

Hard is ambiguous, how hard? Harder than calcium-carbonate? Harder than aluminum? Harder than aluminum-oxide? It makes a difference. I don't know either, but with this one answer we could determine whether it is abrasive to engine surfaces.

__________________

Gone to the dark side

- Jeff

So far we have a claim of unknown origin suggesting 2%.

We have both Detroit & Caterpillar saying 1%.

The OP even has his oil tester suggesting 1%.

Mobil say dont go beyond the motor manufacturers recommended max interval.

http://www.mobiloil.com/usa-english/motoroil/car_care/askmobil/oil_change_interval_diesel.aspx

Some one could post saying they thought they read some place it was ok to go to 15%. Then not be able to find their source.

Its just an ambit statement or trolling.

Does any one have any reputable information that says the target should be more than 1% ? They have not provided it in the past 50 or so posts.

Making an unsubstantiated claim to get a response & then not backing it up with a source is nothing but trolling.

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

I don't think he was trolling, just wanting an answer.

So far, none.

__________________

Gone to the dark side

- Jeff

External additional filters that filter down to 1-3 microns. Not the bypass section in the stock filter.

If you go back and read my previous posts you will see I have said that the hardness is some where between that of graphite & that of diamond. It varies between particles.
Your hardness measurement (moh's) is not relevant to small particles. Individual soot particles can be far harder than white metal used in bearings, even harder that some grades of steel. What we have with a soot particle can be likened to a granite rock coated in rubber. Shear it & the oil coating comes away.

Your comments about oil providing a thin film & so providing a clearance are an over simplification of the surface chemistry & shear properties of the process that occurs. In an engine bearing or other shearing interface, we have a thin layer of oil molecules some attached to the metal, others free to move between 2 metals. At times there is metal to metal contact. if there was always clearance, the 2 surfaces could be the same metal in these shearing situations.
Further your comments about turbines & the comparisons with situations in an IC motor lack technical merit & if one was to review the properties required of a turbine oil compared with a IC motor oil this would be clear.

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

Not trying to argue, just trying to get to the mechanics of soot and its effect.

Hardness is always relevant regardless of the particle size. No matter how small a grain of silica-sand, it will scratch glass. In contrast, a piece of silicone, regardless of size or how sharp its corners might be, cannot scratch glass. A harder substance will always abrade a softer substance.

The turbine I'm referring to is the turbocharger. If soot particles were abrasive to the cast-iron cylinder walls, it would be very abrasive to the turbine blades like sand in a sand-blaster.

An over-simplification was intended, as no more technical terms are necessary IMO. If there is oil, there is clearance. If no clearance, then no oil, and eventually a weld/seize. Lubricants as you likely know are designed for these applications and the shear is designed to maintain a film of lubricant between the (ex: cam and lifter) two components, whether solid or liquid. Similar metals are used, an example being the cam and lifter.

__________________

Gone to the dark side

- Jeff

Some interesting reading (Non-paying info):
http://www.machinerylubrication.com/Read/51/soot-oil-engine

http://www.machinerylubrication.com/Read/1033/diesel-engine-oil-contaminants

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92 300D 2.5L OM602 OBK #59