I have been using AMS for over a year now. I have no way of measuring the difference in performance or protection value of this oil. I am using it in both my cars. One is a summer Solo1 and solo2 race car and the other one is a daily driven VW golf. My question is does AMSOIL provides an added benefit compare to Mobil 1 or Formula 1 mastercraft synthetic oil that cost almost half as much? My mechanic tells me that even the cheapest bargain oil Penzoil, Valvoline quickerstate do the same job on a street driven car if the oil replaced every 5000 KM.