Originally Posted by jerky
My 2003 KENWORTH has a c15 caterpillar 6nz serial number which is pre egr and its oil stays brown til around ten thousand miles, and my 2014 powerstroke which the egr stopped working for some reason has clean oil til about 7,500 miles
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You can thank ultra low sulfur fuel for that.
Whether it's a Cummins, International (6.9 and 7.3 idi turbo & non-turbo, 7.3 di, 6.0), Isuzu, Detroit, Cat, JohnDeere, VW/Audi, ect. that I've owned or work on, the oil ends up black. It may take a little longer nowadays for some thanks to ultra low sulfur. Alot of the DI diesels, even after oil is drained, still have a few quarts of old black oil in the high pressure system so upon startup it mixes with new oil turning it black.
Your Kenworth holds probably as many as 4 times as much oil so of course it will take longer to appear black. Also if you're running a by-pass filter it will help.
As a side note, if the oil wasn't black I'd be more concerned because it's job, among others, is to carry contamination to the filter(s).
To wrap it up it makes no difference EGR or not and black diesel oil is no indication of a problem, it's a way of a diesel's life.