Originally Posted By: dnewton3
All these rated at 20um unless otherwise stated: (data taken directly from OEM websites, product pages, etc)
Motorcraft 80%
AC-Delco 98% at 25-30um (that's how they put it ...)
Purolator basic (red can) 96%
Purolator PureOne 99%
Purolator Boss 99%
Fram XG 95%
Fram TG 99%
Fram Ult 99%
Wix/NG 95%
Bosch D+ 99.9% at 40um (a value that is not helpful in terms of comparing, but all they advertise)
Bosch Premium 99%
Mobil 1 99% at 30um (that's thirty microns, not twenty; not a typo on my part)
K&N Gold 99% at ???? (no stated size; missing info = worthless info)
Royal Purple 99% at 25um
Amsoil 98.7%
The worst I've seen the MC typical filter is 80%, but I've seen other reports stating it's better than the OEM claim.