I asked this question on the Subaru forum that I visit and I got a few opinions but nothing backed up by any real evidence or data.
My 2014 Subaru Legacy 2.5 came with a two year free maintenance that is now used up, so I am doing my first oil change on it. I went hunting for an oil filter. At Advanced Auto Parts, the have a Purolator Classic listed for it, but not the higher grade Pure One. Just for the heck of it, I had them check for the 6 cylinder engine. For that engine, there is a Pure One listed as well as a Classic. When I compared the two, I found that both have the same thread six and the same diameter gasket at the base, but the can for the 6 cylinder is a little larger in overall diameter.
I don’t see any reason why I can’t use the one made for the 6 on the 4 cylinder. The filters are remotely mounted above the engine so clearance is not an issue.
I thought maybe the filter used on the 4 cylinder might be unique to that engine or used on very few engines where the one for the 6 might be more commonly used and that demand didn’t justify the production of a Pure One for that engine, but then I looked through a Fram catalog and found that they don’t make (sell) a filter that fits the 6 cylinder at all in any of their lines, but they carry filters for the 4 cyl in all the grades of their filters.
Anyway, back to my question, anyone know why using the filter made for the 6 would be a bad idea on the 4?
Edit: corrected second paragraph to reflect the can is larger, not the base gasket.