This discussion is a little like, "what kind of oil to use in your oil can...to lubricate your bike chain?"
A more appropriate question is, what oil would NOT work!
As RevKev says, not much going on here....and as those who have responded with nearly everything put in a bottle....it all works.
I would like to be a fly on the wall when you have a failure in the chain case and the dealer denies warranty because you didn't use "HIS OIL".....
BTW prolly should NOT use snake oil.....but even there I am just guessing.
Into the chaincase....go to shelf....kmart oil....fine! End of story....years of no failures says it all. Inside engine...whole different ball game!