Originally Posted By: ZeeOSix
Fixed your typo (in red) to start. This has been hashed over many times. If you have any mathematical background at all, you will know for all practical purposes that as the particle size approaches 20 microns that the limit becomes, for all practical purposes, equal to, or "@20" microns.
When Fram says that their filter removes 99% of all particles >20 microns, then that is saying no matter what size the particles are from 20 microns and greater, for every 100 that hit the media, only 1 gets through. Even if that 1 particle was always 20 microns in size, the statement is still basically true. If the test dust was ALL 20.01 microns in size, and only 1 got through, then you would say the filter is basically "99% @ 20 microns". But since there are particles that are smaller and larger than 20 microns in the test oil, then I believe Fram uses the ">20 microns" statement to make people realize it's catching everything and small as 20 microns and greater. Most consumers aren't to up on filter efficiency and beta ratios, so I think Fram is trying to make it as simple as possible to understand.
If Fram could use the statement "99% at 20 microns and greater" it might sooth the hair splitting dudes that can't quite grasp that 20.01 microns is still larger than 20 through simple mathematical deduction.
If Fram said 20 and greater, then it would be a non-issue. I would agree with you that fram is 99% at 20. However, they do not say 99% and greater, they say "greater than 20". Which logically, is more consistent to say 20 or greater.
Wix could likely say 95% for particles greater than 5 microns... despite only having a 2=6 depending only being 50% at 6 if their sample includes a disproportionately sample of 30 micron particles (either in number or by mass). If it is mass (assuming equal density), then two 6 micron particles and two 30 micron particles could be a 84% efficiency if the filter only removes the 30 micron particles, if it caught 1 of those 6 micron particles (50% or 2=6), then it would be 92% efficiency.
Now, here is where Fram's > symbol is defeated. Assume we take 100 6 micron particles and 100 30 micron particles with an actual beta of 10/1000=6/30 (or 90% at 6 and 99.9 at 30). Thus would result in a combined efficiency of 99.0075% for particles greater than 5 (or 6) microns. You don't have to use special language to account for error when with standard testing at a given range.
That is the problem with stating Fram as 99% at 20 (or 20.01) microns. We do not know the actual beta and a beta of 90% could be going on but is essentially accurate to say 99% if you include the greater than modifier.
I agree that Fram's language is more consumer friendly, but it is less accurate and thus when we make comparisons between Wix's 95 @ 20 vs Frams 99 > 20 we can't make heads or tales. It could be 20.01, or 25, or even 100. We just dont know.
As I assert, it is not that Fram isn't filter 99% at 20, it is that we do not know what fram is filter
at 20 because of their language. Yes, (depending on the instrumentation) as particles reach the target (20 in this case) there should be a "bell" developing that accounts for this. We see this on VOA with some samples having a volatility mass loss of 15.4 when the standard is 15 for SN oil. The oil might still within parameters. However, if the standard says 15 and then another company says greater than 15 (15 or higher), then that is not OK.
