I respect castrol oil. In my opinion, castrol is better than mobil 1.
I am running castrol syntec 5w30 on my 2006 camry v6 with 204,000 miles. It is very very quiet. The car response better.
I haven been using castrol motor oil for 3 years. I start with gtx, gtx hm, now syntec.
syntec is the best investment. I do 10,000 - 12,000 OCI. I change my oil at walmart, which cost $55. I am happy with the price I pay.