I think most of us would agree that most particles 5um or less are fairly harmless overall. But that is presuming that the quantity of those particles is fairly low in overall concentration. There is a big difference between quantity of particles and size of particles.
But there are a few things we need to remember.
1) UOAs ONLY see stuff in the 1-5um range; anything smaller or larger go unseen.
2) UOAs cannot distinguish size of particle; they only account of the concentration, within their visible range
3) While "some amount" of Cu may not be harmful (and perhaps even helpful), exceedingly high amounts of it are not necesarily a good thing.
In respect to the last item, let me be exact. Think of many things in life that are "good" in moderation, but "bad" in excess. Vitamins are "good" but too much "C" or "A" can destroy your liver and kill you. A glass of red wine is reported to be healthy, but we all know that over-comsumption can be detrimental. Some amount of sunshine is good for vitamin "D" production, but too much can cause skin cancer. Get the point? I do realize that Cu is not always a bad thing in a UOA. I do realize that some Cu is occasionaly used as an additive in some oils and treatments. But I also see statistical evidence that TOO MUCH COPPER can quite likely cause other events that are unpredicted and/or unforseen. Ottomatic asked how my database shows the interaction of Amsoil and Dmax engines. Well - that is exactly what I'm trying to get people to hear about. My data shows that there is an 87% chance of elevated Cu above 3 standand devations, and a 69% chance of elevated Cu above 5 standard deviations. (Please note I'm reducing the information to make it consumable. I'm not doing this to "talk down" to people from an egotisical point of view, but there is simply way too much data to put in a consumable format here on this site. I could write a small book about the data collection, distribution, and results on this topic). Yes, all Dmax trucks shed a bit of Cu when new, but that quickly subsides. Unless you use Amsoil, RL, RP, etc. Then the Cu spike are quite large, and hang on for some time. Eventually, the Cu will come back down, but that is not always a quick thing, nor are some people patient enough to wait it out. Also, the spike in Cu is almost always accompanied by a spike in Fe. Now, is it the chemistry of the oil making the Fe spike, or is it the presence of elevated Cu wearing on the Fe? I don't know, but neither do you. We DO know that they often go hand-in-hand (93% of the time in my database). Also, don't forget that the UOA only sees what it can see; if the Cu is 350ppm, how much more Cu is floating around above 5um and below 1um? Remember - some Cu might be a good thing, but too much is likely a bad thing.
Further, just what seems desireable about removing Cu from a cooler anyway? I don't care if it's a "chemical" reaction that some would say is harmless. I am often just a simple man who likes easy analogies. Think of your skin as the barrier it is. If I remove a small amount of skin by the normal process of "wear", your body is prepared to endure for a long time. But if I abrade it with a wire brush, or burn it away with chemicals, do you really give a poo what took your flesh away? As your skin is peeled away, some amount of your protective barrier is removed. It's no different with the Cu in the cooler in my opinion. I don't care if the Cu is stripped away by mechanical friction or chemical reaction; I don't want it removed at all. That is a barrier I want in place. Period. The less removed the better, for me. I DO FULLY AGREE THAT SOME SMALL AMOUNT OF CHEMICAL REMOVAL IS UNAVOIDABLE, AND HAPPENS EVERY TIME WE CHANGE OIL. But I don't agree with the notion that all is well when huge amounts of Cu are present in a UOA, and that is only the Cu we can see in the UOA; how much "more" is being stripped that I can't see??? I fully agree and understand that the bearing are fine; that is not the Cu we are seeing and I understand that. I'm talking about the cooler here, folks. At some point, and none of us probably know what that point is, the cooler is being degraded. Clearly there is no significant failure rate of coolers, or we'd all hear about it. So I would be the first to profess that the point might be moot. But "might be" and "are" are not the same thing. I cannot assure you that this is truly bad, but you cannot assure me that this is truly moot; at best, it's a stalemate.
But what I DO know is that high Cu has two other effects.
1) it clearly affects Fe as well. Probably not to a level that is grossly detrimental, but it's certainly not benign either.
2) high levels of wear metals in a UOA from chemical reactions can mask the metals shed from wear events. At times, the Cu spikes can be so grossly high that you simply cannot see the forrest for the trees. The "noise" from the chemical stripping is easily able to mask other events, and you'd never know it.
To really give a fair synopsis on this Amsoil/Dmax topic I'd have to say this:
* I cannot prove that high Cu is completely detrimental
* I can prove that high Cu skews data ranges and trends in a UOA
* I can prove that high Cu is able to mask and hide other events due to the magnitude of the element present
* I can prove that high Cu is accompanied by other elevated wear metal counts (Fe)
* I cannot distinguish at what level Cu stops being "helpful" and starts being "hurtful", but we all understand that at some point, that transition does take place
* Amsoil states that these "chemical" reactions are not harmful
* Amsoil states that they cannot explain why the reactions are stronger in some units, but not others
* Amsoil cannot prove that these reactions are not detrimental
* I would agree with Amsoil that the Cu is likely from the cooler and not from bearings, but since I don't use Amsoil, and have never done a teardown on a Dmax engine to measure bearings and visually review them, I cannot say this for sure
