Hi, I'm using a 50/50 mix of 10w40 Castrol GTX and 5w50 Castrol Syntec. Alfa recommends 10w40 but I've been using 20w50 before this. Is my oil mixture ok? I think it is better to use a mix of Syntec and GTX rather than the Syntec Blend, though I have nothing to back up my claims. Thank you Zamani ------------------------------