Switched to synthetic oil in my older Cummins, now I'm second guessing myself

I run a 2007 5.9 in my shop truck and decided to try full synthetic at the last change, 15w-40 rotella T6. After 3,000 miles the oil analysis came back with higher copper than I've seen in 8 years of using conventional. My buddy in Tulsa says the older seals just don't like it, but another guy swears it's just flushing old deposits. Anyone else see a spike in wear metals after switching, or is this normal for the first run?

1 comments

1 Comment

the_dylan17d ago

Man, that copper spike would freak me out too, but my old 12 valve has been through worse abuse than a Walmart parking lot. First synth change on mine showed a little extra metal and then it leveled right back out, so my guess is it's just the detergent doing its job and stirring up decades of crud. Your buddy in Tulsa might be thinking of the old seal shrinking issue, but that's more of a gasser problem from what I've seen. If the copper is still up at 6,000 miles, then I'd start sweating, but one sample is just one sample. Give it another change and see what happens, that's way cheaper than a rebuild.