I haven't really installed a new filter in my 2004 WRX in a while. It's my understanding that it generally doesn't do much damage, although it might possibly create a restriction. However, when I look at the typical dirt collection patterns on the pleats, it's only a fraction of the filter that loads up. The edges of the pleats seem to collect the most dirt, but then in certain areas the dirt collects deeper into the pleat. I found this photo online, which is typical of what I see:
The Subaru OEM filters were almost the same design over the years. The factory installed one was made in Japan and red. I bought a bunch of OEM filters (made in USA) from a dealer years ago and eventually ran out. The filter color was more yellow but still effective. Then the OEM seemed to be made in Mexico but looked as good as the others. But they were always lightly oiled and had a metal frame where there was some paper label on both of the longer sides of the rectangle.
I'm thinking maybe aftermarket. I've seen the various rectangular box filters from Fram/Wix/Purolator/house brands and they seem to be simpler ones made of unoiled paper, no frame, a foam surround, and maybe a screen. Any issues with installing something like that vs an OEM?
The Subaru OEM filters were almost the same design over the years. The factory installed one was made in Japan and red. I bought a bunch of OEM filters (made in USA) from a dealer years ago and eventually ran out. The filter color was more yellow but still effective. Then the OEM seemed to be made in Mexico but looked as good as the others. But they were always lightly oiled and had a metal frame where there was some paper label on both of the longer sides of the rectangle.
I'm thinking maybe aftermarket. I've seen the various rectangular box filters from Fram/Wix/Purolator/house brands and they seem to be simpler ones made of unoiled paper, no frame, a foam surround, and maybe a screen. Any issues with installing something like that vs an OEM?