How railroads did oil change/replenishment was not the point I wished to make. The point was that their method was highly controlled and repeatable. The average tractor/machinery owner does not follow such strict protocol, so the lab analysis of motor/lube oil is not as meaningful and can be very misleading. But I promise you that metal in the filter is meaningful and the only way you're going to find that out is if you cut that filter open and look.Maybe for you, not for me. Far as railroads go, in EMD engines the lube oil is never changed. It's sucked out, centrifuged, additives added and back in it goes. I spent a lot of time at Electromotive before they closed the McCook facility. I hauled cranks for Park Ohio Industries (Ohio Crankshaft) to Electromotive 2 times a week for years
Just sayin'....