Ed, I am reading your post as explaining why a particle count isn't necessarily going to correlate with wear metals in a UOA. When you say
Quote:
This is one of the many reasons why "wear metals" do not serve as a good indicator of wear. The ICP only sees a portion of "normal" wear and miss most if not all of the larger particles generated by abnormal and break-in wear. The other is that due to the different densities of the metals the instrument does not see them equally. Given an equal amount and distribution of particle sizes, the ICP could read 4X as much aluminum as lead due to the density difference between the two.
I think you are saying that "ICP is not a good method for determining engine wear," or "ICP is not a good method for determining the amount of wear metals in an oil sample." I think part of the confusion--and here I'll just speak for myself--was that a particle count was understood as demonstrating how well a filter was protecting an engine from wear, in that fewer particles counted, equaled less engine wear--or at least, that this was why a particle count was included. I'm not saying anyone spelled it out like this, but this is usually how UOAs are interpreted---lower iron ppm usually means less engine wear, and so on. I suppose I was viewing the OP in the same light as a UOA.
My take now is that a particle count (and Dr. Dave's results) simply indicates that fewer particles in the oil, mean that the filter has to be doing a better job, because if it wasn't, then more particles would be in the oil. A drop in iron, copper, and lead in the oil (in terms of ppm per thousand miles) sounds more impressive to me, than by a drop in particles found in the oil, but if I had to pick between fewer particles of varnish and less in my oil, sure I'll take fewer particles.
If I am misunderstanding things, feel free to let me know. Just speak to me about ICP & particle count as if you are trying to teach Shakespeare to a caveman, and I think you're approach will be just fine.