AMSOIL Expands the Signature Series Line AMSOIL Signature Series Synthetic Motor Oils deliverextraordinary lubrication in all types of automotive gasoline engines. By combining industry-premier synthetic technology with AMSOIL premium additives, Signature Series Synthetic Motor Oils exceed the higher performance demands of modern engines. New viscosities to the line up are 5w-50 for specific Ford Mustangs and 0w-40 for Chrysler and Nissan. Please check with us to see if your vehicle can use one of these new viscosities.