It's not rediculous. It's reasonable and proven science. Allow me to explain. And I'll admit that I'm not a paid tribologist. I'm not Doug or Terry. But I am a statistical process quality control engineer, so I do have some fairly good basis for understanding the methodology involved.
I'd be the first to agree that one UOA does not prove much, but many successive UOAs can show trends and ranges that will announce abnormal wear.
RL and RP tend to have greater wear metal numbers in a UOA. They will claim that it's "chemistry" based reactions; they could be right. But the problem with inherrently high wear numbers as a base-line is the ability of those same high readings to mask and/or obscure events that would be easily recongnizable with lower "normal" readings. The magnitude of the ppm change due to some event can be shaded by the % of change. Products like RP and RL mask those numbers because they carry high residual nubmers. That's just plain old math; you can't argue that. Yet RP and RL will tell you that's "normal". Perhaps, but only from their perspective. I would prefer my wear metal counts to be as low as possible, allowing for immediate identification of subtle changes.
Further, it depends upon how you want to argue the point of "wear". There is big wear from major events, and there's small wear. But size of particles and % of particles are not always the same thing. A UOA can tell us PPM, but not the size of the particles. RL and RP would have us believe that higher chemistry wear will be mistaken for true wear. But where I come from, the shedding of particles it typically just "wear", regardless of it's origin. If a dog poops in your yard, are you going to argue about it's size and origin? It's undesireable, regardless of where it came from or how big it is. Regarding chemical wear, it's still metal components shedding particles from their place of origin. I don't care if they are big or small; I don't want them leaving the bearing, the cylinder, the crank or whatever. In that sense, high wear PPM counts from RL or RP indicates that there is metal leaving metal.
I completely acknowledge and agree that teardown analysis is the only TRUE way to know how well a lubricant has done. But that process presumes that:
1) you have used that same fluid brand/grade for a long period, to exclude other variants.
2) you have (nearly) unlimited time, money and resouces to tear down your engine, tranny, diff, or whatever.
For most of us, a UOA gives reasonable insight into the world of lubricants, if we understand their benefits and their limitations. UOAs are NOT the panacea of lube knowledge, but they are a supporting chunk of it. UOAs can directly advise you of your lubricant health, and indirectly advise you of your equipment health.
This whole thread started because someone (an admitted synethic junkie) want's affirmation of his use of RL. They want to know if 10k miles on a PSD is doable. Well - maybe so, maybe not. A UOA should be able to tell him. My point is that a VOA only predicts how the oil might behave; UOAs tell you how it actually performed. Looking at some VOAs or PDFs is not near as informational as seeing UOAs.
UOAs can certainly show wear. And at times it's not "normal" wear, but catastrophic wear. I recall a post on another site where we helped diagnose a problem with grossly high wear numbers. The poor chap had plumbed his Amsoil bypass system backwards, and was getting nearly zero flow to the engine! Here, a UOA certainly was instrumental in quickly pointing to a problem outside the contribution of oil itself, but the oil was the "carrier" of the information.
Perahps that better defines my view.
