All the talk about oils and what you can and can't do is not a big comfort. I have read and heard from numerous sources to use 30wt, non- detergent oil in my c10 235. I was told that the rings would not seat properly using detergent oil but I never understood why that would be true. I dumped the 10w30 after a hundred or so miles of trailing blue smoke, but it still smoked for a while with 30wt non detergent .. It did eventually quit smoking.
I have also read that the detergent multiweight oils do not have zink additive which will cause camshaft lobe failure in older engines.I have noticed a couple of articals about cam failure in racing engines that do not use oils with a zink additive. Chevrolet engines back in the 50's and sixties experienced came lobe failure but I never heard then of it being attributed to the absence of zink in the oil. To my knowledge, Ford engines of the same generation never experienced the cam failure. I remember hearing "Chevies have soft cams".
Because of posts in this chain praising Shell Rotella, I went to Walmart and read the specs. They do not say it has either zink or ZDDP. They not even say it is for use in gasoline engines; they only specifically mention being for diesel engines and "other heavy machinery". Then I read the specs for the 30wt non-detergent oil I had bought to put in my truck. It specificaly says DO NOT use in automobiles newer than 1930 or possible engine damage may result. Now there is another comfort.
I think I'm goimg to switch back to Valvoline 10w-30 which I have mostly used for years.
The owners manuals for a lot of 4 cycle lawn mower engines specify non-detergent oils. I have seen electric motor driven air compressors and other types of pumps using crankase oil lubrication specifying non-dtergent oils. I have never head a reason for this, I suppose there is one somewhere.
meansam

1960 Chevy Stepside