I'll just say this much: I know of a certain 1997 Suburban that has had Maxlife changed at least every 3,000 miles since 170,000 miles. It is now at 420,000 miles and doesn't leak any negligibly greater amount than it did when its diet was changed to Maxlife. So excuse me if I, personally, ignore the naysayers for HM oils in an engine that doesn't leak. It may not be as necessary but I've seen no physical evidence that it does any harm.
Last edited: