Join Date: Jan 2006
Location: Lawrence, KS - Rock Chalk
Car Year: 2010
Car Model: Legacy 3.6R Limited
Back in the day before there was a turbo Impreza/forester motor here there was one filter and it was 80mm in diameter. Then when they introduced the turbo motor here in the Impreza they fit the same 80mm filter on there. They later discovered that the way the turbo's exhaust manifold was designed, the filter was so close that during extended idle times, the oil would get cooked. Because of that in 04 they started specifying a smaller filter, it was 68mm and shorter too. That gave the proper clearance to prevent the oil from getting overheated in the filter. At that time the NA filter was white and the turbo one was black. Since all things were pretty much equal, later Subaru said to simplify things just use the small one on both the NA and Turbo motor. So in reality since there was room you cold use both the larger and smaller diameter filter on the NA motor but not the larger one on the Turbo. Like I said the smaller one did actually have more filtering capacity so it was all good. Since then they have gone through a few different suppliers the latest being Honeywell (AKA Fram) or the blue version. So it's kind of hard to say if they have once again gone to another vendor with a different looking filter using the same specs or it is indeed (due to the new motor design) a whole new filter set of specs and filter. Until we hear otherwise it's of course best to go with the OEM specified filter for the 2011 as you are saying.
2010 Leg 3.6 R, 2013 OB, 2001 OB, 2001 Forester S and 1999 Miata