I was pricing Valvoline Premium Blue today. While I was at the Napa store near my house the salesman told me that the Napa 15-40w was the same oil as the Valvoline Premium Blue. Any one have an insight on this. I have been running Chevron Delo 400. I am going to switch to Valvoline Premium Blue. The Valvoline was 13.99 and the Napa oil was 9.99.