Did forget to mention my religious use of Redline fuel additive. It is used based more on conventional wisdom passed on to me from others then any scientific facts.
I carry several bottles in the trunk and use the recommended dosage with every fillup -
(1 bottle will treat 10 fillups of 20 gallons.)
I am not certain this will reduce soot contamination of the engine oil, however.
One more item of importance is regular valve adjustments (if the engine requires it, as is the case with the 617.xxx engines)
Just had mine done and the engine is purring at idle with the minor rocking completely eliminated.(Thank goodness it wasn't something with the injection pump.)
And the mechanic enjoyed the MB wrenches I loanded him, purchased at the Parts Shop.
Maybe I'm imagining this but there seems to be a reduction in exhaust belching as well.
I do agree that sticking with CG-4/CH-4 rating is a good idea irregardless of what brand oil is chosen.
Hope I didn't stray too far from the oil soot topic, but thought maybe smoke belching and oil soot may be related ? I'm not sure...