Let me clear up a myth - Except for Mobil 1, AMSOIL, and a couple of other PAO based lubricants (group IV basestock), there is no such thing as synthetic oil - other than those three and a couple of others, synthetic oil is nothing but highly refined and dewaxed mineral oil (group III stock) with enough additives to meet Diamaler Benz-Chrysler and Chevrolet Corvette specifications. Group III oils calling themselves synthetic include U.S. Castrol Syntec, Texaco Havoline Synthetic.