Somewhat related: In high school I had a 1961 GMC fleetside pickup with a 350 and a 4 speed Saginaw, I thought winterizing it would be the smart thing to do starting with a flush & fill on the cooling system. I knew my buddy that I bought the truck from had not done this previously as I was his mechanical advisor. Going through Dads stuff in the garage I remembered a can of boiler cleaner I had seen, and figured it would do just as well if not better than the automotive type cooling system flush. It did quite well, even removing some block sealer that had been hiding a crack in the #8 cylinder wall
. Motor oil sure looks like frothy melted mocha ice cream when it's whipped with fresh Prestone.