most of the time I don't use any oil at all so far all my OS engines are fine,I have 7 OS engines and I also live 3 blocks from the Ocean.
when I store a engine I will use 3in1 oil and plastic bag it to keep it clean but have used WD40 and it is also a fine moisture barrior,the can says it protects from moisture and prevents rust thats what the after run oils are suposed to do is all.