Gary,
I wouldn't worry about your copper at 7 ppm, or your tin at 3 ppm. Those numbers are low.
I have a general chart for the Cummins engines, and based on a
"Normal" Drain interval, which would be around 10,000 miles, Copper (Cu) levels of 40 ppm would be at the condemnation level. Tin (Sn) levels would be around 10 ppm to be considered condemned. Of course the longer time on the oil would change the numbers.
Also, If you had a high number of copper, and a low number of Chromium (Cr) the copper would not be coming from the bearings, as the last metal element to go on a bearing is Chromium (Cr). The copper is under the Chromium. High numbers of Copper in our trucks often come from the oil cooler located just behind the OEM oil filter.
Here is what the chart shows based on the "Normal" drain interval:
Iron= 50 ppm
Chromium= 10 ppm
Lead= 25 ppm
Copper= 40 ppm
Tin= 10 ppm
Aluminum= 10 ppm
Nickel= 8 ppm
Silicon 20ppm *
*Over oil Baseline
**Levels will also vary due to operating conditions, component age and manufacturing differences in.
Wayne
amsoilman