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Old 12-24-2021, 10:37 AM   #26 (permalink)
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Originally Posted by clarknova View Post
I own some IDI engines and a common-rail. All of them have black oil, despite a disabled EGR and oil catch can. AMSoil sells a bypass oil filter that claims to remove soot and it's on my wish list.

We have a large mechanically-injected Cummins generator at work and the oil always looks pristine. I'm not sure what the secret is. Maybe because it never runs above 16% load except during semi-annual maintenance.

I drove a 2015 school bus with a Cummins 6.7 for two years and I never once saw the regen light turn on. Probably because I drove a rural route. I don't recall if the oil was black in that one.
The oil in diesels turns black quickly regardless of EGR as the raw particle emissions are pretty high and contaminate the oil.
Interestingly the opposite can be observed in CNG/LPG vehicles where the oil takes a long time to darken.
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