The A&P who did the annual on our old club Fly Baby started out as a mechanic on Northwest Airlines Constellations. He told me to use MMO on my Fly Baby's Continental to help forestall valve problems. And I have, for the past 30+ years.
Oh, and it has kept the hangar clear of elephants, too.
I posted a story of my old A&P to the Fly Baby web page:
http://www.bowersflybaby.com/stories/legacy.html
Ron Wanttaja