"Amsoil SSO was a more recently approved oil. " Not really. Amsoil says SSO is "recommended" (by themselves!) where HT-06 is called for. Amsoil constantly plays the game of recommending their oils against certain manufacturer specs without actually stating that they MEET the specification in question and without getting the sign-off of the original equipment manufacturer. SSO is a great oil, and it may or may not actually meet the UNPUBLISHED requirements of HT-06. BTW, I also am very annoyed by unpublished manufacturer special lubricant requirements. They are playing that game more and more, and the only reason for not publishing the special technical requirements of various lubricants is to maximize marketing and co-marketing advantages.