Why would engineers go to the trouble to design a 4 ring piston, and produce rings for it, if it wasn't necessary? Actually, that third "compression" ring is a "scraper" ring that seals compression on the upstroke, and flexes to catch any oil that the main oil control ring misses on the downstroke. Of course, those engines were designed to work for a living, not ride a trailer to a car show a couple of times a month!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!