http://forums.vwvortex.com/zerothread?id=313674&page=4 Thanks to Primus for the link. In this thread, this debate was about M1 SS using a grp III still in it's formulation. Notice Mobil says synthetic bases stocks "Including PAO". Could this explain why the volatility is a bit higher then Amsoil/RL? NOAK for both of these oils is 5%. I thought this issue was laid to rest. This link though is a bit old.