I've been thinking of mixing 2 qts. of GTX Start Up (the U.S. version of Magnatec) 5W-20 with 3 qts. of GC for winter use in my 2002, 2.5L Outback. (Easy, PScholte . . . easy, Big Fella! . . . easy Elves! ) The result would be a 2W-30 instead of a 0W-37 which is roughly what GC is. The purposes would be: 1) to reduce GC's 37 wgt. to a legitimate 30 wgt.-- since my 2002 Outback calls for an XW-30; and 2) accomplish no. 1 by combining a complementary lighter weight oil with GC (the GTX S.U. having the prospect of adhering to surfaces much like GC coats engine surfaces). Anybody know of a Castrol tech. who could tell me if these two oils are chemically compatible? I want to use the GC in my Outback, but I really don't want a 40 wgt. (almost) oil for the O.B. BTW, do we know if the Gold has the same heavy-30+ wgt. characteristic as the green? Maybe I'm worrying for nothing???? My six qts. are from the M0504 run, making them Gold.