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.

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