Mr, Broken head,
I agree filters are economically necessary in your field as in the marine world. I would presume the oil gets black because your working w/ Diesels only. That black's been normal for a hundred years. Probably modern engineering will curb that. I've not dealt w/ Diesels for years now. The rings are asked to do more than they can handle, including cavitation. Efficient injector pressures and spray patterns, correct Pump timing are crucial. Operators often have no clue how to operate/run a Diesel, also. Here, I believe the subject was gasoline powered 216-235 types. There's no reason for one of these to get black oil in 2-3000 miles of normal use. Yes,poorly coordinated engine mods, unusual driving habits,etc will affect the oil's condition. Black is a serious indicator of fuel contamination.
Just for fun: Chev did offer spark Diesel 216s? late ''30s called Hesselmann.
David
