I have been a synthetic oil user for many many years but change my oil at 3 to 4 grand. I have now decided to go with syn blend oil. The reason i'm going with a syn blend is short trips and cars sitting for 1-3 days without use. Currently i have 5w20 synpower in the focus and 5w30 synpower in the vq35 altima. I am a very big fan of valvoline and have used durablend before. I have also used syntec blend. It seems that castrol is not favored here and i don't know why because it's an great product. Durablend and syntec blend, any insight on which to use now? I have used 5w20 syntec blend early in my focus' life and it seemed to love it. Don't know how real the sensation was.