On the advice of a highly-respected rotary mechanic in town, I have always used Mazda's oil filter in the RX-7. He told me that was the safest thing to do because of the higher oil pressures in the rotary, and Mazda's filters are designed for that.

After much research, I chose either Mobil 1 or Amsoil filters for my non-rotary vehicles. What say everyone? Will you stick with Mazda?

BTW, here's a link showing the guts of many popular filters, along with some commentary on each...

http://www.scuderiaciriani.com/rx7/oil_filter_study/

and

http://www.frankhunt.com/FRANK/corvette/articles/oilfilterstudy/oilfilterstudy.html

same info, i think, but different format.