A question that I am not sure how to even ask...

They used to sell quarts of "motor flush" at auto parts, which was basically kerosene if you read the ingredients. You drained your oil while hot, filled a quart of that and let the engine idle for a few minutes. I did that in my 69 Dart slant (dumF kid then) and maybe a month later the oil light came on while driving cross-country. I now think that gunk clogged the pickup screen. Today, most I would do is fill the pan with kerosene, but not start the engine, and let is sit for a week, maybe with a heater under the pan, then drain.