Even a 2 micron Frantz bypass filter will not remove the black color from oil from a Diesel engine. The PM procedure on the engines I serviced included a filter element change at 15K mile intervals, top off the oil level with about 1 1/2 gallons in a 15-gallon system, and never change the main sump oil. Analysis of oil samples was done by an independent lab at every filter change, and even after 100K miles on the oil, it was still passing accepted standards for contaminant levels. The owners of the fleet were suitably impressed with their cost savings for PM service.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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