Just an FYI, I just ordered AMSOIL 75w110 Severe Gear. 4 quarts for my trans, 1 quart for my rear diff.
I thought long and hard about this and I won't truly be comfortable until I experience it. Subaru owners who have messed around with different gear lubes (such as AMSOIL, Redline, or "cocktails") report substantial benefits to shifting, NVH, and gear whine on engine braking over the stock fluids, Mobil 1 75w90, etc.
So I'm hoping for all of the benefits, long life, drivetrain protection, and none of the negatives people have experienced with the "cocktails".
AMSOIL has treated me right so far with their TSO 0w30, SSO 0w30, and MTF ... all in my Civic SI.
I hope it continues that way!
Joe