ohyea, i dont recommend Castrol Syntec to my friends because it's not a truely synthetic formula. it's actually a derivative of mineral oil that's been put through a 'special', and i'm sure 'patented' process. (a bunch of garbage if u ask me) it costs the same as mobil1 and amsoil per quart, but is not a true synthetic?? where's all the extra money go to? the patent office or their marketing department?
ohyea, and who cares if it's 5-50w, just choose an oil for the climate in which u live. your not going to keep oil in the motor for an entire year anyways.