Something I inquired about not too long ago, never got a conclusive answer from members here but I've always been somewhat skeptical of oil analysis in general. According to this, high Fe or Cu doesn't necessarily mean high wear, and one should not be quick to conclude oil performance based on wear numbers without knowing all the details of the UOA.
http://www.lube-tips.com/
http://www.lube-tips.com/
quote:
The time when an oil sample is taken is an important factor in obtaining representative and trendable oil analysis data. The optimal time to take the sample is during the machine's normal operation, because after the shutdown, all the particles begin to settle. The rate of settling is defined by Stoke's Law. Here is an example of how quickly some particles can settle four inches (assuming spherical-shaped particles):
50-micron silica particle: 12 minutes
50-micron steel particle: 2.1 minutes
50-micron copper particle: 48 seconds
50-micron chromium particle: 2.5 minutes