I think you’re misunderstanding my post. I’m certainly not arguing that short OCIs on even “run-of-the-mill” oils will result in dirty engines… quite the opposite. If the oil is not run past one of the many condemnation points that can be determined from UOAs (TBN, insolubles, oxidation, etc) it’s certainly possible for the engine to live a long, happy, clean life… similar to
@dnewton3 ‘s experiences.
However, if the oils are run past their capabilities and start leaving deposits in an engine, mineral oils and even most synthetics can’t really clean varnish and coked leftovers. Those kinds of deposits require ANs and esters to chemically dissolve the deposits.