Originally Posted By: LoneRanger
Something interesting to note is that in model year 2006 two things happened with the 2.5 liter four cyl engine: Subaru made i-AVLS (intelligent-Active Valve Lift System) standard equipment, and they specified the smaller size filter as the OE filter.
One other thing happened at the same time: They changed they exhaust routing on the NA H4s. It wraps around the oil filter, just like on the turbos. There is not enough space for the older, larger filter.
For the older NA H4s (2005 and earlier), the Purolator Pure One PL14460 fits and the bypass valve is spec'd at 20-25 PSI. But it has no anti-drainback valve.