The OP claims he/she has a 2010. IIRC, it was the last MY for the EJ25 in the non-turbo U.S. Forster; Subaru spec'd 5W-30.
FB25-equipped Foresters with 0W-20 synthetic oil started with MY2012.
Jim / crewzer
12 Forester 2.5X FB25 5MT Premium AWP PZEV
09 Forester 2.5X EJ25 5MT Premium AWP PZEV (sold 7/2011)