2018 Chevy Duramax L5P - 6,400 miles 37,800 miles total - Oil not changed

Jun 3, 2003
BC, Canada
To attempt to draw conclusions looking at just one element in this case copper, would be short thinking. Rather one needs to look at the combinations and what they represent to the mechanical device we are sampling. Copper by itself is a known observation of cooler leaching. If there were copper, lead, and tin in combination then it would point towards bearings. This is clearly not the case with Wayne’s sample. What Wayne is doing is correct. If he had high Silicon, aluminum, and Iron clearly you would be looking at the induction side for the path of the dirt reaching the cylinders and generating wear. The OLM is an algorithm which does not pick up the fact that Wayne installed a higher performing non commodity lubricant by which the algorithm was based off of. Oil sample data is the only way to establish the correct drain for his oil in his vehicle.

We publish a TBN of greater than 13. It routinely will run 14.8 at the lab Wayne sent his sample to because the method they use will catch all the base. Wayne is in a safe area and it will be interesting to watch his sample data going forward.

BTW. Wayne that was a great article you found. I would also point out that leaching from the cooler is not just relevant to Diesel engines. I see this very same thing in gasoline engines and many industrial applications that have coolers in the system. We see spikes if someone changes a cooler, then like your sample data it tapers off. Changing oils can also effect the sample trend as you see on your truck.
I found the same trend with my 2011 LML. I finally got the copper down after 8 years by not switching brands all the time.