Mr Broken head, It's just not been my 64 yrs of eng building experience to have the oil even discolor much in 2-3000 miles, let alone turn black in a proper gasoline engine. Engs of the past, yes, but they can be rebuilt using today's tech. As mentioned earlier,poorly tuned, short run driving, not up to block, head and oil temp for an hour or more, lots of cold starts and driver habits will cause the darkening. It's a clue that something's wrong with the picture that needs investigation. Years ago, maybe 40,a Chev service bulletin I read described that old low pressure, high volume Chev designed oiling system had operating conditions in mind. Dirt road dust in most of the country would get into engines. Combine that w/people wouldn't change oil very often and oil quality was as pumped from the ground. Not like today's oil at all. Chev didn't want the dirt forced into the working surfaces. The idea kept these engs running when many other small oil passage, high pressure types lost brgs and shafts. Last week I dismantled a 1963 Palmer marinized 308" IH. Everthing in it sparkled. Rocker arms, inside cover and pan looked as new. It was running the simple, canister, remote, small flow filter many seem to misname as bypass. That 308 would have been dirty by average thinking. She powered a fishing hull 48 yrs. Once fired in AM., it'd run all day. Best scenario.
Mr. Lincoln, the eng lube system maint you describe is popular w/ the fishing fleet w/ frequent sampling analysis. These are all Diesels. I don't like that procedure for gasoline engs because of the oils aromatics diminishing and oil thickening. The sump volumes are small and are affordable to dump when prudent. David
