Just walked through Castrol Syntec product data sheet.
It reads Castrol Syntec 0w-30 meets A3/B3/B4 spec, but in the following data HTHS only reads 2.9. All syntec series only 5w-50 reads 3.9 higher than 3.5, others all lower than 3.5.
Back to the list of specs met, 0w-30 (GC), 5w-40, 10w-40...