To the OP.

Everyone has a favorite way of doing things. Some like this fuel,engine,radio,oil, whatever. Avoid running lean, use a fuel/oil combo that you like, with the required oil content stated in the manual. It never hurts to run 20% where 18% is the minimum. Synthetic oils are fine,castor oil is fine.

The truth is not very many people actually know what oil is the best. I do know that castor is the accepted long time standard, it has proven itself. The synthetic oils are just not trusted by a lot of folks.

I myself have used full synthetic,a blend, and full castor. None of them have ever harmed an engine of mine.

I personally use an after run oil, lots of others do not, their engines are just fine.