Ive read that when on auto-rx youor supposed to use a good quality filter, aka Moblie1, purolator pureone. However, they are on the oil flow restrictive side... how important is flow then, when on auto rx? What about using fram extend guard, seesm to filter down to 10 microns and offers outstanding flow! or maybe even K&N? How about CFM oil filters, i called them, and they filter down to 7 microns! Not sure abut its flow though, expensive filter too! $100, then you have to buy refills. Any ideas?