Originally Posted By: The Critic
Originally Posted By: jkhawaii
the Subaru Synthetic appears to be a Group 3 oil similar to the Amsoil OE line (from Subaru's site "A synthetic base oil can be produced by using two different processes. Both processes start with crude oil) Amsoil Signiture is 100% Synthetic PAO oil not based on Crude oil.
Is the Subaru oil, the venerable high-VI stuff? If so, it may be superior to the PAO oil for most drivers.
Unfortunately the SN version of the Idemitsu oil is not a high VI oil; IIRC it's only 169 vs 197 for the SM oil that Mazda, Mitsubishi and Honda/Acura Canada use. Plus the SM version is high in moly.
I believe that the Toyota (Scion) version of this car spec's the TGMO 0W-20 which has a ultra high 216 VI, so I'm sure that oil could be used without any warranty issues.
As far as Amsoil is concerned, as mentioned the XL 0W-20 is a better choice since it's an API oil unlike the signature series and is lighter and therefore closer in viscosity to the spec' oil.