Originally Posted By: JAG
A commonly seen example of dissolved metals are the oxidized copper streaks often seen below copper gutters or copper roofs. Acid rain can greatly accelerate the dissolution. Likewise, acids in motor oil can do the same. Reactions besides acid types also can cause metals to chemically react and end up in the oil. The particle sizes of dissolved metals tends to be very small (with exceptions) so spectrographic analyses accurately measure their concentration. Rubbing wear in an engine produces some particles too large to be completely ionized and therefore detected in spectrographic analyses. Underestimation of their concentration results. So 300 PPM of copper that was caused by being dissolved in the oil can equate to a mass loss less than another oil sample with copper particles all of a size of, say, 7 microns, that a UOA test said the concentration was, say, 20 PPM.
Metals in an engine other than copper also chemically react. In the case of iron, one way to determine an estimation of iron particle size profile is to get a PQ index test done. It's not as cheap and easy for a lab to do a similar test on non-ferrous metals.
I find myself questioning all that logic ...
I'll agree that UOAs cannot see all the particles; they can only see 1-5um in size generally. However, that leaves me pondering your explanation. Whatever "wear" particles that are present above that 5um size would be present in any type of fluid regardless of base stock and additive package, would it not? So one cannot use a UOA to predict the performance of any lube? Are you saying that ONLY particles from chemical reactions show up in a UOA, and none of them are from wear? I disagree. I do acknowlege that spectral analysis is only a portion of the window of knowledge, but it's short sighted to say that a UOA cannot predict and/or speak to "wear".
Think about this for a moment. The typical statement in opposition to my position is that high Cu counts with no accompaniment of Pb or Tn means the bearings are fine. But to take JAGs possition into account, that would also mean NO wear particles were present, and only chemically stripped particles were present. Does that not become a self-fulfilling prophesey? I see high Cu, but no Pb or Tn, so because they are all so small, none of it can be wear? So often I've read that if high Cu is not also seen with high Pb or Tn, then it's ok. That infers that Pb and/or Tn due to wear are not present. If that were not the case, then would we not just believe that JAGs comments of UOA particles being chemically induced would apply to all? Preposterous. So if we can see Pb or Tn as wear in a UOA, then we can surely see Cu as wear, in addition to chemically stripping, in a UOA.
Why ever do a UOA then? if all particles are due to chemically stipped origin, how do we predict wear? Are we supposed to do an annual tear-down of the equipment to measure bearing clearances? If JAGs proposition were true, then we would not be able to use a UOA to predict wear. The whole point of a UOA is to establish ranges and trends for wear particles BEFORE the event gets so large as to be catostrohpic. We want to catch the few particles in a UOA that show a undesired trend outside of the normal limits, statistically speaking. That in mind, we are trying to find particles in the 1-5um range that shows "normal" operations, so that large jumps in quantity can predict "non-normal" trends. I completely agree that some wear particles are outside this viewable range, but that also means that some are inside the visible range. It's important to note that UOAs see quanity, but cannot distinguish size. PCs, OTOH, an distinguish size, but not compositionb. In a UOA, I'm not looking for a particle size, I'm looking for particle quanity within a specific size range. An statistically significant elevation in ppm means more particles are presnt, indicating a "non-normal" event is occuring.
This concept is practiced not just in lubes, but medicine. We look for small changes in PSA rather than waiting for prostate cancer to become painfully evident. We look to shifts and overall quantity in cholesterol rather than waiting for the heart attack. Get the point? We cannot see all the big events due to the scope of the tool, but we surely can look for "normal" and "non-normal" trends at small magnitudes, hoping to avert the big disaster.
Jag stated this:
Rubbing wear in an engine produces some particles too large to be completely ionized and therefore detected in spectrographic analyses. Underestimation of their concentration results." I'll agree with that, but only because he's defined it well. But he left out the "yeah, but what about the others ..." topic.
I agree that rubbing wear produces some particles great than 5um, but that can be said regarless of the lube used. And "underestimation" can result. If "some" of the particles are above the visible range for a UOA, then that means that "some of them are NOT above that visible range. IOW, "some" of them ARE visible in the UOA, directly due to wear. I agree with that too. But agin, that is true regardless of the lube used. It does NOT explain why some lubes such as RP, RL, Amsoil and others wish to pass this phenomenon off as desirable. If it's not desirable, then it must be undesirable. You either want it to happen, or you don't. There is no middle ground here.
Further, if the ONLY use for a UOA were to predict "chemical" Cu, and not wear, then why do the UOA, ever? In fact, why do a UOA when ever using one of the premium products? If you are "only" going to see chemically stripped Cu, why do a UOA when using that oil? Oh - but wait - there is the famous "well, the Cu will spike but then drop back down after the reactions settle". OK - I agree with that, and I've seen the evidence of it. But is that not a recogniztion and acknowledgement that UOAs have a purpose PAST seeing chemically stripped Cu? Isn't that a resounding statement that "wear" can be seen when "dissolved" Cu isn't present? It that were not true then why does anyone do a UOA. And if it IS true, then it speaks to the fact that during that time in which Cu is elevated from chemical attack, the detrimental effects of wear are going unnoticed because the magnitude of wear is lesser when contrasted to that of chemical chelation. You guys cannot have it both ways. You cannot fairly state that UOAs don't see wear particles, but we should use them after the chemical reactions subside. It's either a valid technology for predicting and noting wear patterns and lube performance, or it's not. I say it is.
And, like I've pointed out in other posts and threads, the high Cu counts associated with the phenomenon have the ability to mask otherwise detectable events.
I completely agree that the Cu chelation phenomenon is typically not detremental in it's sole existence. But I find fault with the fact that one might conclude "all is well" because of the other side effects of the topic.
