Is the mobil 1 filter for synthetic only or is it just as effective for conventional oil?

btw, I was searching and found this http://www.ntpog.org/reviews/filters/filters.shtml , which makes me wonder why people still prefer oem? The North American oem filters that were dismantled and shown were not well made.


[Modified by gsr.sedan, 2:35 PM 3/27/2002]

 

There was a another similar test done like that in another website with a bunch more filters.

The conclusion on those are very judgmental, and it is more of an opinion than scientific result.
I presume that all those manufacturers are 9001 certified, all meeting SAE requirements, so I think any of those filters will do its intended job.