2021 Chevy Duramax L5P - 9,750 miles/239 hours on oil - 31,300 total miles/734 total hours - HPL 5w-40

As another poster mentioned after 100k they really seen the copper trend to nothing substantial. Although I'm going to assume yours will be higher than a lot if you're using it to tow exclusively. Is this all tow miles?
Towing is about 75% of the miles. We do use the truck locally, because it is our wheels when on the road.

It's great to have these discussions. Where else in the world can we spend so much time & have this much fun :p
There is no place like BITOG!
So you'll run this oil out to 20k miles again? Your Fe at 9700 miles is where it was at 13,500 previously. You might hit your 100 ppm Fe limit around 15k miles.
Yes, I will sample again at 15k and plan on running the oil to 20k. Mr. Newton, Mr. Ward, and I had this discussion at the open house about how much Fe is too much. Mr. Newton suggested that the absolute amount of Fe shouldn't be the condemnation criteria, instead the rate of Fe/1k miles is much more important. Keep in mind that this sample started at 16ppm Fe from the previous run. If we see the rate increase significantly, then that is cause for investigation.

@dnewton3 @High Performance Lubricants
Are we sure the copper isn’t some kind of AW additive?
I know they are ‘old school’; but HPL seems to go back to tried and true old-school technology..ie high metallic additive use, high ester use…