I have watched differential pressure rise on every engine I have worked on that actually has a differential pressure gauge installed. (meaning the filters are getting plugged by something, only rarely is it any thing you can actually see) Granted most of these were at the smallest, 1200 horsepower Cat V-16's to (the biggest have worked on) 7500 horsepower enterprise V-16's. After 35 years in the field I would not run an engine (or any machinery for that matter) without a filter, I would not remove one in any case. If your engine is so scrupulously clean, why does the oil get black?
