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Don, the oil in the newer diesels, the ones with the low emissions, like the 6.7L Dodge, 6.4L Ford, and the 2007 (most) and later GM 6.6L will show the oil as black about five minutes or less after you start the engine after an oil change. That's just the way it is. If you figure out how to tell when the oil needs changing, by looking at it, please let me know. I can't see a change like I could in the old days.
Don, I'm not an expert but have read many times that the quality of today's oil is so much better that oil changes at 3,000 miles today are a waste of good money. However, that's the opinion of those who wrote those articles. I sure don't have the knowledge to debate that point and won't try to do so. All I know is I took the advice of many who had the experience with synthetic and after running synthetic for somewhere around 150,000 miles (3 different trucks) I see no reason to not let it go to 10,000 miles. However, the true test isn't at that mileage, it's at the upper end, just how long does that engine really last.
Rich has a very valid point about warranty. A Dodge dealer told me, when I asked, that 10,000 on synthetic won't void my warranty, so long as I can show the receipts for the oil purchase and mileage at the change. However, should I have a warranty situation, I would be at his mercy that he remembered telling me that (didn't ask for it in writing) and that Chrysler and Cummins would agree. So the dealer's "word" I have to take only as advisory and not commitment.
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