Okay heres the deal in my 04 big dog manual it says we DO NOT recommend synthetic oil and in my 07 manual it suggests using only a premium 20w50 v-twin oil. S&S recommends Mobil 0ne symthetic oil. Both bikes I own are S&S and I run amsoil. Can you lighten me why Big Dog does not like Synthetic oil? just like to know there reasoning behind this Thanks JOE


