Originally Posted By: dlundblad
How can a filter rated at collecting a 29 micron particle grab a 20 micron particle? 20 is smaller than 29 right? I would assume any size smaller than 29 microns wouldn't get caught and continue to pass through the media. Regardless of efficiency. I think I need schooled on oil filters 101.
A filter doesn't work the way that you (apparently) think it works. Just because a filter is rated at 29 microns (for instance) doesn't mean it will pass every particle smaller than that... nor does it mean that it will catch every particle bigger than that. Any given filter will catch a fraction of particles down to fractions of a micron. Furthermore, as a filter loads up with debris, the debris will effectively become part of the filter medium, only passing smaller and smaller particles on average.