Ive tried Various Synthetic Oil, All are good untill they reach the 3K mark. Oil start to deteriorate thus engine being less quieter and harder to accelerate.
Here are some oils that i tried and how far it can go before it performs less(performance wise, not sure about protection).
(1) AMSOIL – 10K {0w-30 Signature Series, can run up to 15K or 1 year}. @ 10K its still quieter and accelerates better than other oil at 3K. – My fave
(2) ENEOS – 4K {Super quiet. Smooth and fast acceleration on stop and passing on the freeway, also on hill climbs. FOR PERFORMANCE} – My 2nd Fave
(3) ROYAL PURPLE – 3K (quiet than and better performance than others below this line}
(4) Mobil 1 – 3K (same as other oil i tried)
(5) Castrol – 3K (same as other oil i tried)
I have not tried Penzoil,Quake etc….
This is just an input on personal experience.