Use DELO 15W40 or some other diesel-rated oil year-round. The engine was designed and clearanced for SAE 30 straight weight oil in the summer, and 20W-20 in sub-freezing weather. Water-thin modern oils will make it sound like there's a bunch of little guys with sledgehammers inside trying to pound their way out. DO NOT use non detergent oil in any engine- - - -save it for lubricating door hinges, etc.
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!