what is the difference between when a engine oil meets performance vs approval?I see that Castrol Syntec 5W-20 is approved in my Jeep Hemi but Castrol GTX/Synblend meets performance.In the past GTX was approved because it was on their site and on the bottle.Is this because Castrol is testing these oils (GTX/Synblend) with the new Tri-Shield formula?On their site there is a asterics next to GTX and Synblend.Thanks Joe