★★★★★ 5
Comparison with POTAUTO filter: Very similar but cheaper
I bought a POTAUTO MAP 1033C and EPAuto CP846 cabin air filter to compare them for use in my 09 Legacy (gen 4). They both seemed comparable and are cheaper than most other, similar filters, though the POTAUTO was and still is ~33% more expensive than the EPAuto.
Both seem built well-enough, considering they're only being used as relatively low-flow cabin filters. That said, the EPAuto is slightly better, mainly due to the white trim piece being unattached along one side on the bottom of the POTAUTO filter. Almost certainly nothing that will affect its performance or longevity, but it is interesting considering it's the more expensive of the two. However, it must be kept in mind that this is an incredibly small sample size.
In one of my very scientific tests (/s), I held them up side by side and looked through them toward the sun (obviously being careful) to judge thickness/density and uniformity. Neither had any thin spots that I noticed, and they were pretty similar overall. One of them blocked slightly more light than the other, indicating more filtration, but I unfortunately don't remember which one. I feel like it was the EPAuto, but I don't really want to speculate as I could very well be wrong. What I do remember is that the difference was so minor that all else being equal, it wouldn't justify the cost difference between the two. In other words, even if the POTAUTO were the slightly better one, it wouldn't be worth the extra few dollars for the minimal amount of extra filtration.
In another test, I compared the filters to each other and the old filter (which I'm pretty sure was OEM, but certainly not a charcoal filter, so it was significantly thinner) by blowing air from a compressor through them. I held the nozzle at roughly the same distance from each on one side of the filters, and I held my other hand at roughly the same distance from each on the other side. The old filter, unsurprisingly, let much more air flow through. Both charcoal filters were much more restrictive due to their extra thickness, leading me to feel much less air coming through. Both were roughly the same. Both filters also held up just fine to the strong blasts of air.
I bought a couple other filters that I was going to cut to fit to use one or both with these filters as a pre-filter and/or additional charcoal layer. After the airflow test, I decided against this, as these are a lot more restrictive than OEM already, and I didn't want to push it, since that could at best cause issues with getting good airflow into the car, and at worst could damage the blower. If not for the fact many, many people have been using these and similar filters for a long time without apparent issue caused by this, I would hesitate to even use these. I haven't noticed a decrease in the airflow, but it's doubtful I would since I rarely turn the fan up past the first couple settings (usually have it on the first) if I have it running at all, and I have the center vents pulled out (to access the inside of the dash) which causes the flow at the vents to be reduced slightly.
TL;DR - Both the POTAUTO and EPAuto charcoal filters appear to be a good choice, with the EPAuto having a slight edge on build quality (based on my limited sample size of one each) and a cheaper price. Filtration appears to be very similar between the two, certainly not enough of a difference to warrant the extra price for the POTAUTO over the EPAuto. Flow is significantly more restrictive than OEM filter but doesn't appear to be an issue. I give the EPAuto 5 stars and the POTAUTO 4 stars, only because the value of the POTAUTO is a good bit less (very similar or possibly even inferior quality for 33% more money). I can't speak to their longevity or performance, but I don't imagine either should prove to be an issue.
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As a side note relating specifically to the Legacy: replacing the cabin filter in this car is a PITA. It's not overly difficult per se, but a serious pain and certainly not something you're going to do when you have a spare few minutes. I'd rate it probably around a 3.5/10 in difficulty and a 7/10 for annoyance. While you can sort of access it by removing the manual compartment, you can't remove the tray through that. So you need to actually take the whole glove box out, which requires removing the side panel, unhooking the string/loop that keeps it from falling all the way down, and removing a few plastic screws, which can be a bit of a pain (and apparently Subaru loves them since they're all over the car). A stubby Philips driver will be helpful. Once you have the glove box out of the way, you have to unscrew several more of those plastic screws to remove the plastic cover between the glove box and the filter. This hole is where you gain access. Be careful when removing the old filter as loose dirt and debris may fall out and make a bit of a mess. You don't really want to get any in the fan below it if you can help it. Reverse the steps to reassemble it, and remember to reattach the string. Getting the glove box back in its track can be a bit of a challenge; in my experience from doing it multiple times I've found you sort of half force it and half don't. That is, it'll likely offer some resistance even if it's lined up, so if you try to baby it you'll probably be there a while, but also play with the alignment a bit to see if you can get it without marring up the tab and the slot on the right side too much. All in all, expect to spend anywhere from 15-45 minutes on this, and make sure you have a standard length as well as a shorter or stubby Philips screwdriver. I have to say, when it comes to air filters, this car is horrible. The air intake filter is a pain to change, too--much worse than most if not all other cars I've done.
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Keywords: Subaru Legacy, fourth gen, fourth generation, 4th gen, 4th generation, 03, 04, 05, 06, 07, 08, 09, 2003, 2004, 2005, 2006, 2007, 2008, 2009
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Reviewed in the United States on September 29, 2017
