Not sure of that statement unless you could show us in writting.
Synthetic is best by far. And Amsoil is proven to be the best out there. No one matches or beats their protection or offers a warranty as extensive as theirs.
Want to know more... email me. I can get you dealer pricing to your door. 0w30 works great in our cars. I have it in my Audi 1.8t with mods and my '83 GTI. I get 8% better gas mileage with it too!