[Scott.T]

10W40 Part Synthetic, it's whats recommended by Subaru so good enough for me.

I put Mobil 1 Motorsport (not the 0W40 stuff, something like 15W40) Fully Synthetic in mine for 2 weeks and took it back out as cold starts sounded like a bag of nails.
Engine had only done 18,000 miles and has now done 50,000 (almost).

IMHO alot of the fully syth talk is pub talk.
if car is doing heavy track work then yes spend the money, otherwise stick with £15-£20 part synth as recommended by Subaru and change at least every 6,000 miles