Best oil, is controversial, as well as opinion based. How I found the best oil, was reading here on BITOG, then forming my own opinions. What I feel is best means nothing to anyone else, and could probably start a small war.
My three favorites (unfortunately not all OTC oils), in random order, Pennzoil, Amsoil, and Schaeffers. These are strictly based on my reading BITOG, please also note I have only tried Schaeffers #132 additive as of today, but I am confident from my reading here that it would be a favorite oil if I used it. JMO