I believe there is no Group 3 0W-20 oil so they should be all 100% Full Synthetic. The Subaru 0W-20 is by Idemitsu and it's not the same formulation as the one for Mazda.
For example, Castrol Syntec sold at VW/Audi stealers here is Group 3 (they went to Castrol EDGE when the higher output 2.0T came here so not sure if this is still Group 3 <cough> not enough ZDDP / cam follower failure causing <cough> oil), Motul 8100 is PAO base stock which is Group 4, Motul 300V is ester base stock which is Group 5.
I know for a fact that Mobil 1 off the shelf here is not the same Mobil 1 stuff you get in Europe from Porsche dealers.
From
http://www.bobistheoilguy.com/forums...opics/950311/1:
"There was not and never has been any suit AT LAW regarding the use of the term "synthetic" for Group III base oil, and no court or ALJ has made a ruling on this matter. Mobil simply filed a complaint with the National Advertising Division of the Better Business Bureau in the US claiming that Castrol was engaging in false advertising by calling Syntec "full synthetic" since it was now being made with Group III base oil. Castrol was able to present enough "evidence" to convince the NAD that Group III base oil could legitimately be called synthetic, so they rulled in Castrol's favor. This ruling has no "legal" standing. It merely means that as far as the NAD is concerned, an oil company is not falsely advertising an oil as "full synthetic" if that oil is made from Group III base oil."