I found this site a few years ago http://www.frankhunt.com/FRANK/corve...lterstudy.html
and I thought I should share it.
It raises some interesting questions about OEM and brand name filters. As a consequence a few years ago I cut open a variety of Australian made filters (K'Mart, Ryco, Pwer Plus, Valvolene etc) for the Fords and my Mitsubishi Lancer (Z56B) and they all appeared identical inside which suggests they were all made by Ryco (which isn't surprising as it was originally established in the 40's as I recall to service the then new Australian Auto manuafacturing industry). Some had different style rubber flap valves but the internals seemed to be from the same source.
I've stayed with Aussie filters ever since about 20 years ago one that was made in Thailand came off while I was driving along just after it was fitted. When I opened that one up it was apparent that it was made from recycled tin cans (the label of some canned fruit was till on the inside). While I'm sure the Asian filters have improved (and I bought some cheap ones to open when I opended the other ones up and they seemed OK both inside in terms of filter length and valving and outside in terms of steel quality etc). And I guess "Made in Australia" doesn't necessarily mean the filter medium was made here anyway; it could be just assembled here,
Being a stingy type I opended my filters after I'd used them using an oldstyle spike type can opener. It is a messy and time consuming job and having satisfied myself that most Aussie built filters were OK lost interest in opening any more. I'd like to open up a genuine Ford one and compare it to a Ryco one some time and would be interested in what anyone else has found in pulling filters apart.
The Aussie ones I've opened seemed to be of a similar design to the Wix/Dana Corporation ones with a large by pass valve spring in the base.