I'm not here to debate Mobil's marketing, only say what I experienced.. I was not expecting much. only a better oil than what I had been using, which the old stuff was shearing down way too quickly in an engine that is not hard on oil. But I saw Mobil 1 clean up the patina/varnish on my 96 Civic in one oil change! I was looking into the oil filler hole for the valvetrain. Sure, I didn't have sludge at all in the Civic's engine so I can't test that claim. But to clean up the patina/varnish that was there for years (28 year old engine at that point) was something that surprised me!