Hi!
Your'e right! Running in is not rocket science! If you just avoid some of the pit falls like dirt and running lean our engines will just run and run and....
But the modern synthetic oils we have in Europe are better than castor oil in that they don't leave a lot of residue (black stuff) on the piston wall and combustion chamber.
Try them and you will never go back to "Old castor oil" for ordinary sport engines (Racing engines are a different matter). I do miss the smell due...there is no synthetic oil that smells as good as castor oil.

Regards!
Jan K
Sweden