john40

I'm confused. What is the difference between nominal and absolute micron ratings? I'm currently running an auxiliary Wix 33528 fuel filter rated at two microns. Is this an accurate number?
Thanks-John

C Schomer

The difference is several microns. Absolute is the larger size the filter will trap at 100%. Nominal is the smaller size the filter will trap but at a much lower percentage. I don't know how they come up with the exact numbers for the nominal rating. I only believe independant tests. Filter mfgrs jack with their numbers something terrible! Craig

Thundercraft

mostly agree - Absolute is 98.7%.

Nominal, like you say is a smaller particle size - but it's a useless rating as there's no real test criteria to come up with that rating.

Why do most filter mfgrs us nominal (remember, if they don't say it will be a nominal rating) ratings? Probably because it makes their filter look better than it really is.

What you want to know is what is the micron rating that the filter will probably pretty much clean up everything vs. what is the particle size it might catch.

john40

Thanks for your replies-John