you can get a 5layer or 2 layer now.. one has carbon etc in it.
My subaru says every year or 7500miles...lol Its getting the shop vac at those intervals.. My hyundai wasnt even dirty at 18000miles.
Its a 5min job... they want something amazingly high for it..(like 79$) I'll pass on that
from the manual
Air filtration system
Replace the filter element according to the
replacement schedule as follows. This
schedule should be followed to maintain
the filter’s dust collection ability. Under
extremely dusty conditions, the filter
should be replaced more frequently. It is
recommended that you have your filter
checked or replaced by your SUBARU
dealer. For replacement, use only a
genuine SUBARU air filter kit.
Replacement schedule:
Every 12 months or 7,500 miles (12,000
km) whichever comes first