Engine Oil viscosity
 

Sorry if this question has been asked a 1000 times...

I'm just about to buy a load of Mobil 1 synth engine oil, which is the best viscosity to get for use in a MY03 WRX PPP ??

5w-30 as recommended in the manual as 'preferred' (??)

or

15w-50

Any ideas what viscosity a dealer uses for a 10,000 mile service on a MY03?

Ta,

Chris.