Expand for the bold part. That is what I'm trying to say with the "grace period" wording I used. When contamination of the oil reaches a point of excessive wear with a less efficient filter or efficient one. Not that it has no wear at all. I think the same as you about clean oil. But I'm not going to say it's some fragile oil that can't stand some level of debris without causing excessive wear to the engine. Just trying to add more clarification.
Contamination with what? And how is any oil fragile as compared to the level of debris? None of this makes any sense.Expand for the bold part. That is what I'm trying to say with the "grace period" wording I used. When contamination of the oil reaches a point of excessive wear with a less efficient filter or efficient one. Not that it has no wear at all. I think the same as you about clean oil. But I'm not going to say it's some fragile oil that can't stand some level of debris without causing excessive wear to the engine. Just trying to add more clarification.
The oil itself will perform the same in terms of performance parameters associated with the oil viscosiy and formulation regaurdless of the level of debris in the oil - all others factors affecting oil performance being constant.Expand for the bold part. That is what I'm trying to say with the "grace period" wording I used. When contamination of the oil reaches a point of excessive wear with a less efficient filter or efficient one. Not that it has no wear at all. I think the same as you about clean oil. But I'm not going to say it's some fragile oil that can't stand some level of debris without causing excessive wear to the engine. Just trying to add more clarification.
I don't understand this?
Yep, an efficient filter & good oil are good combos along w/severe oil change interval should cover most. Taking the guesswork or long term UOA testing out of the equation.
The tool doesn't have the resolution to allow you to draw that conclusion. There are so many factors that influence the ppm numbers that spectrography presents, it's like you trying to determine my waist size from a sample pulled 10 miles downstream from where I pissed in the river.
There is a certain level of contamination required to start causing a meaningful increase in wear.
If you look at all the UOAs in the "Used Oil Analysis - Gasoline" forum, the wear metals are way above 1000 miles on long OCIs. Keep in mind that everything that ends up in the oil is not from external dust making its way into the oil. Wear metals from metal-to-metal contact and combustion blow-by also contributes to oil contamination and additional wear debris. And the longer the OCI, the more contamination debris build up and wear metals ppm there will be.
What would be interesting to see in this case (for example) is what does 50 ppm or 200 ppm of 0-5 micron test dust equate to on an ISO 4406 particle count per mL of oil. Did the study have any data correlating test dust particle counts to ppm of test dust? Based on the looks of the graphs, the study looks relatively old.From a study that intentionally contaminated an engine's oil sump with varying concentrations of dust, wear increases roughly linearly with dust concentration above 10 ppm, but at 10 ppm, wear is only 1.6 times higher than the baseline with no added dust. Dust in engine oil at the end of an OCI should usually be < 1ppm with good air filtration and paved-road driving. The difference in wear between, say, 0.01 ppm and 1 ppm should be insignificant.
Wear metals tend to be a lot more abundant than dust, but it's possible that they don't cause as much wear for a given mass of contaminant, due to differences in abrasiveness or particle size. If wear metal particles tend to start out a lot smaller on average than 0-5 micron dust, it would take a lot more metal to start causing significant wear.
I think filtration is more important on long OCIs, but I don't think this has to do with abrasive wear. If an engine eventually pulverizes any particle large enough to cause wear, wear-causing particles wouldn't keep building up in the engine over an OCI. Sub-micron particles would keep building up, and may still contribute to issues like sludge formation.
It's SAE 680536 from 1968. They didn't do particle counts on the used oil. Since ISO 4406 only measures >4 micron particles, and dust larger than that would be broken down by the engine, the test would really only pick up wear metals and other contaminants anyway.
If it's assumed that what ends up in the oil is wear metals and carbon/soot from the combustion blow-by (assume no dust for this discussion), then how much of the particles per mL that are 5u and below are the wear metals seen in the UOA, and how much is "other" debris created inside the engine? In other words, if you look at the OP's UOA for for the steel mesh K&P oil filter, there were 72,235-18,904=53,331 particles per mL that were between 4 and 6 microns. Some of the meal wear particles that size should be detectable by UOA. So if the iron ppm is 4 ppm, what does that equate to in terms of particle counts per mL?
The wear particles detected by the UOA are 5 microns and smaller (some info says up to 7u are detectable). Did those detected wear particles start out that size, or did some start out much larger than that, and the particles not filtered out got pulverized after circulating over and over through the oiling system? Also, the MOFT can get very small in certain components of the engine ... especially in components running a lot in the boundary layer lubrication realm. Even the MOFT in journal bearings can get very thin, even very near or even zero depending on running conditions. Most engine wear studies say that most wear happens from particles less than 10u.
One study that used busses in real world service (the "Bus Study", SAE 902238), where there was no added debris to the sump like in this SAE 680536 test, it showed a good relationship between filter efficiency, oil particle counts and engine wear. The bottom line will always be that better filtration results in cleaner oil, which results in less engine wear ... even in real world engines.
My problem with the bus study is that they equate the amount of wear metals in the oil with engine wear. At a minimum, they should be looking at the wear metals trapped in the filter media as well, and adding this to the total wear metal count.
In the Cummins test, it's unclear if it was done with or without oil filtration. The more efficient the filtration is, the more wear will be biased to smaller particle sizes. There's a radioactive tracer study that measured wear vs particle size with no oil filtration, and found that 10-20 and 20-40 micron particles were most damaging. (SAE 650866)
The Bus Study was real world field testing, as was the testing done in SAE 881827.
I don't recall what kind of UOA they used in the Bus Study. If it was more sophisticated than a spectrographic type of UOA then it could have has a much larger particle size range detection.
I'd think the Cummings wear particle size vs wear rate was most likely without filtration because if it was filtered that would skew what they were trying to measure, which was the effect of particle size on wear rate of different engine components that operate at different MOFT. The filter efficiency effect was included in the real world field testing of course to see the impact of oil filtration level on engine wear.In the Cummins test, it's unclear if it was done with or without oil filtration. The more efficient the filtration is, the more wear will be biased to smaller particle sizes. There's a radioactive tracer study that measured wear vs particle size with no oil filtration, and found that 10-20 and 20-40 micron particles were most damaging. (SAE 650866)
Another interesting aspect of this test is that it shows the effect of larger particles getting pulverized into the 0-5 micron range within the first hour of engine operation.
They performed separate tests with each type of dust. The dust samples had the same total mass, not the same number of particles. The 0-80 micron dust was "Standardized Fine Air Cleaner Test Dust", probably based on old SAE standards but similar to modern ISO Fine A2, which has a fairly linear distribution by mass.
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