[m6pwr]

The best info I've ever read on understanding used oil analyses appeared in the May 2012 issue of Tribology and Lubrication Technology magazine. It's an article titled "Used Oil Condemning Limits". Unfortunately this is not a mag you'r ever going to find on your local news stand. It's the professional journal of the Society of Tribologists and Lubrication Engineers, and the article has been archived and is no longer available online, so I can't provide a link.

One of the things the piece emphasizes is that the limits used by the various oil analysis labs are very conservative. The only realistic condemning limits are the ones developed by the oem's (car mfrs) and their lubricant partners through lab testing and field research. These limits are not published but they are incorporated into the oem's oil life monitors and maintenance schedules.

I've been told by a lubricant engineer who has worked for Mobil that the iron condemning limit used by Daimler Benz for most of its passenger cars is 150 ppm. So Sapper M3's iron is 21 ppm. 21 ppm iron is N-O-T-H-I-N-G.