Star polymers?? They are not used these days because of their deposit-forming tendencies. Oils cannot pass the turbocharger tests with them. Moreover, Shell doesn't make additives. The additive company Infineum is jointly owned by ExxonMobil and Shell.
Originally Posted by RDY4WAR
As a note, Shell's star polymers are also pretty rock solid when it comes to shear stability. I wouldn't worry about RTG holding its grade.