Opinions are like "noses", or other body parts that smell- - - -and some of them are pretty stinky!
When I was growing up in the 1950's, most of the stovebolt engines used straight SAE 30 oil in the summer, and 20 weight in the winter. Detergent oil was a relatively new development. The conventional wisdom was "Don't switch from non-detergent oil to detergent- - - -it will make the engine use oil". All the detergent really did was clean up a worn-out engine, and let the rings collapse by cleaning the carbon deposits out from under the rings.
Multi-weight oils like 10W-30 don't thicken as they get hot, they just lubricate like the heavier oils as the temperature rises. Using a 10W-30 in an old engine results in less cushioning between parts, and a somewhat noisy engine. I like 20W-50 to retain the thickness of the 20 weight oil, while giving the cold-start flow characteristics of an oil thinner than straight 30. Just my opinion- - - -flame away!
Jerry
