Most of you will probably already be aware that the Tokyo Roki 15208AA160 "black" filter that comes on Japan-built Subarus is not available in the USA. US Subaru dealers replace it with 15208AA15A "blue", made by Fram, at the first oil change. It's widely understood that the Roki filter is superior. Subaru fans have been buying Mazda N3R1-14-302 Tokyo Roki filters, intended for the RX-8, in the belief that they are the same filter as the Subaru 15208AA160. But are they? I decided to find out.
Here we have a disassembled Subaru black next to a disassembled Mazda filter.
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I don't have a fancy-pants filter cutter like the rest of you experienced fanatics; I'm an inexperienced fanatic, so I opened these with an angle grinder.
They certainly look identical at first glance. The external dimensions are the same; the baseplate is the same. Internal construction is the same, with the same anti-drainback valve, and the same steel spring plate holding the filter cartridge down. The filter cartridge is the same length and diameter, and contains the same number of pleats (55), joined with a metal clip.
The bypass valve is spot-welded into the filter end cap:
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So far so good. But we know that Subaru guys are laser-focused on the bypass valve pressure. How to compare that? Hmm.
I put each filter cartridge in a cup on a scale and zeroed it:
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I put a piece of blue tape on a driver:
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Then I pressed down the bypass valve with the driver until the tape touched the end cap, and noted how much force the scale showed. I don't have pictures of this, because I only have two hands. You'll have to take my word for it. The Subaru filter took 5lb 6.2oz of pressure to open the valve to the tape, and the Mazda filter took 5lb 5.7oz of pressure. I would consider those results within the range of measurement error or manufacturing tolerance. Looks to me like it is the same valve. (Please note that I am not saying these are ~5-6psi valves. These numbers don't mean anything except for comparison to each other.)
So are they the same? Well, there is one difference. The center core is different. Here's the Subaru:
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And the Mazda:
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I didn't disassemble them to count the holes, but my eyeball estimate says the Subaru filter has about 50% more holes than the Mazda. What I don't know is whether that makes any difference. I took a look at a few other filters I have on hand (Champ, Wix, Baldwin, Purolator Tech, and Subaru blue) and the perforations in the core vary, but none of them have as many holes as the black Subaru pictured here. So I'm going to guess it doesn't matter, but I'm sure one of you guys will set me straight if I'm wrong.
So, assuming the core perforations are a difference that makes no difference, then my conclusion is that the Mazda N3R1-14-302 is functionally the same as the Subaru 15208AA160, is built to the same quality, and is a good choice to replace the USA-unavailable Subaru filter if you want the closest thing to what the engine was built with.
Just for a fun comparison, here's a Subaru 15208AA15A "blue" filter cut open:
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That's a Fram or I'll eat dirt. The less said about it the better.
Comments are welcome.