5w-30 or 10w-30 castrol

[James430]

I am wondering if I should put either 5w-30 or 10w-30 Castrol Syntec oil in my '06 wrx. I live in New Hampshire and the weather lately has been 32-45 degrees.

[irvin787878]

if i understand it right the number before the w is cold-start viscosity you would be best to refer to the owners manual to make sure your in the temp ranges for your area and type of oil

[mudferret]

A 10w-30 is a more viscous oil, absolutely no reason to run it at anytime in an '06, especially in winter.

[Donkey]

??What oil should I use??