I don't think you are understanding my question and why are bringing up the old "do a search" or contact the manufacture spiel? The search function doesn't work good and what is this place for if someone else can't answer a question maybe even from memory?
It is my understanding that a filter's "micron rating" is what micron the filter has a beta 2.
Micron rating
See bolded part.
Quote:
A filter that is marked or rated "10 micron" has some capability to capture
particles as small as 10 micrometers. However, when you see a filter marked "10
micron", you do not know exactly what this means unless you also have a
description of the test methods and standards used to determine the filter rating.
The results from the different test methods may not be comparable as their
methodology varies greatly.
The two most popular reported media ratings are a nominal micron rating (50%)and an absolute micron rating (98.7%). A nominal rating usually means the filter's
media can capture a given percentage of particles of a stated size. For example,
a filter might be said to have a nominal rating of 50% for particles 10 micrometers
in size or larger. An absolute micron rating can be determined by single-pass or
multi-pass testing and is usually obtained by passing a test fluid containing
particles of a known size through a small, flat sheet of filter me
So the question is isn't the P1 50% efficient at 5 microns so giving it a nominal rating of 5 microns? I already know that the P1 has an absolute rating of 99.9% at 20 microns. The reason I ask is say you are asked the "micron rating" of your oil filter on an oil analysis like OAI does, don't they mean the nominal rating?
So is the filter micron rating question on the oil analysis nominal or absolute? Nominal makes a lot more sense and would be more useful to them. And isn't the P1 50% at 5 microns?