DeliveryValve-
I am far from an expert on the subject, but as far as I could tell, some of your links are to studies in gasoline engines. And it may be that conclusions for gas engines are not identical as for diesels, due to soot loading concerns.

__________________
1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).

The idea that I'm pointing here is that 3,000 mile oil changes are bad for a motor and keeping it as long as you can will provide a benefit. Even though these links are for gassers, the theory behind it is the same for diesels.
Soot over 2% should be a concern. Roy stated earlier, at 9,000 miles, his worst soot load is at 1.5%. Depending on the TBN, this oil still has the potential to go further. But in the end, Roy has his change interval spot on where I think it should be without doing any UOA. Between 8,000-10,000 miles


.

__________________
1983 123.133 California
- GreaseCar Veg System