Thanks.

It really begs the question, that is not possible to answer without much more data, regarding the wear caused by soot. If 1% soot causes a specific level of wear, will the wear be double that amount with 2% soot?

It's a rhetorical question as I do not believe anyone has a good answer for it.

I agree completely about the coolant contamination in the oil. That's the kiss of death.

There are lots of interesting studies out there that try to address Brian's rhetorical question. For instance, Google Scholar came up with the document below. Full copies are not available for free unfortunately. Two highlights from the abstract which many here will hopefully appreciate: 1) EGR accelerates wear on diesel engines and 2) wear increases proportionally to soot loading in the oil.

Sato, H., Tokuoka, N., Yamamoto, H., and Sasaki, M., "Study on Wear Mechanism by Soot Contaminated in Engine Oil (First Report: Relation Between Characteristics of Used Oil and Wear)," SAE Technical Paper 1999-01-3573, 1999, doi:10.4271/1999-01-3573.

Abstract:

Increase of soot contaminated in engine oil caused by EGR system accelerates the diesel engine wear, especially in the valve train. Wear of metal is affected by many factors such as concentration and diameter of soot, oil film thickness, oil characteristics, etc. Effects of soot on metal wear were discussed from the point of view of soot concentration, and soot diameter and oil film thickness. Wear test was carried out by using four-ball wear tester. Consequently, it was made clear that wear increases proportionally to soot concentration, and relation between oil film thickness and soot diameter plays very important role in wear mechanism. Further, the surface of wear scar was observed by SEM to discuss effect of soot diameter on wear and existence of abrasive wear by soot and its occurrence conditions were suggested.

Thanks. I never realized such a document was available and that they confirm a linear relationship between soot and wear.

Almost, but not quite linear
 

BC-
I was able to find a similar document for download via my school library. It is by some reliable folks at WVU. I turned one graph from their pdf file into an image, so I could post it here. It is a bit small, so let me know if you want me to upload a better version. The wear is not quite linear with soot, and I just didn't want to misinform anyone. The reference material is below.

Effect of diesel soot contaminated oil on engine wear
Sam George, Santhosh Balla, Mridul Gautam∗
Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown 26506, USA
Received 28 February 2006; received in revised form 22 September 2006; accepted 13 November 2006
Available online 6 December 2006
Abstract
Contamination of lubricating oil by diesel soot is one of the major causes of increased engine wear, especially with most engine manufacturers
opting for Exhaust Gas Recirculation (EGR) technology to curb oxides of nitrogen (NOx) emissions. The diesel soot interacts with engine oil
and ultimately leads to wear of engine parts. Factors which can change or modify the characteristics of the soot surface are expected to play an
important role in controlling the interactions with soot. Hence, it is important to study the interactions between soot and oil additives in order to
develop high performance diesel engine oils for engines equipped with EGR.
Astatistically designed experimentwas developed to study the effects of soot contaminated engine oil on wear. The variables that were considered
were the base stock (groups I and II), dispersant level, and zinc dithiophosphate (ZDP) level. The above three variables were formulated at two
levels: low (−1) and high (1), which resulted in 23 matrix (8 oil blends). In order to study the non-linear effect of soot, it was considered as a
variable and was tested at three levels: low (−1), medium (0), and high (1). This resulted in testing of 24 oil samples.
A three-body wear machine was used to simulate and estimate the extent of wear quantitatively. The extent of wear was measured as the actual
loss of material, in grams. A second set of experiments were performed on a milling machine (ball-on-flat disk setup). The wear scars formed
on the steel balls were examined using a scanning electron microscope (SEM) and were analyzed qualitatively to determine the effect of soot
contaminated oils on wear.
The results obtained were analyzed using the general linear model (GLM) procedure of the statistical analysis system (SAS) package to determine
the significance of variables on wear. The analysis indicated that wear increased nonlinearly as the amount of soot increased. Cumulative wear
was more for samples with soot contamination than without soot contamination. This showed a detrimental effect of soot on the oil blends wear
performance. The SAS analysis showed that the base stock and soot content were the most significant variables affecting wear. Dispersant and
ZDP levels were also found to be significant. The highest wear resulted from a sample that had 4% soot.

Oh, and sorry for hijacking your thread BPDave. That always seems to happen with an oil-related thread, but it is no excuse.

they had a university study on diesel oil,1 Cummins 5w40,2 rotella15w40,3 rotella 5w40, thats the honest truth
I use Cummins now in both my om617.951 and m104

http://www.peachparts.com/shopforum/...c-sootwear.gif


This graph is rather interesting.


Although the curves are approximately linear, the slope of the curve is quite flat. Using the upper curve, the wear at 1% soot is .0039. The wear at 2% soot is .0044. This represents a 13% increase in wear for a doubling of soot. That's a decent tradeoff, IMHO, and it suggests that running 2% soot as a maximum is hardly detrimental as compared to the traditional 1% limit.

Based upon this data, I'll seriously consider raising my OCI above the current 5K.

Just to add more links as to why Changing Oil Often leads to more engine wear.

Long term UOA test results.
Mobil 1 Test Results


SAE white papers.
The Effect of Oil Drain Interval on Valvetrain Friction and Wear

Antiwear Performance of Low Phosphorus Engine Oils on Tappet Inserts in Motored Sliding Valvetrain Test

Raman Characterization of Anti-Wear Films Formed from Fresh and Aged Engine Oils






3,000 mile oil filter changes are too frequent. I think 61x and 60x filters should be good up to 7,500 to 10,000 miles. But a UOA on the specific engine will tell for sure.


.

Hmm
 

It is a personal choice.


.

Of course it is.

Some personal choices are well-grounded. And some are not.

very interesting thread…plus all the external references are excellent.

Slightly off topic – what is the general take on using a pre-oil change engine flush?

I use lubro-moly engine flush around once every year. I figure they’re a reputable manufacturer, and reason this makes sense especially with a longer oil change interval.

What do believe you are "flushing" once the oil is drained?

Absolutely agree.

It also has a beneficial effect for Luqui Moly.

DeliveryValve-
I am far from an expert on the subject, but as far as I could tell, some of your links are to studies in gasoline engines. And it may be that conclusions for gas engines are not identical as for diesels, due to soot loading concerns.