Originally Posted by Diesel911

You can thank DeliveryValve for prompting that particular thread.

In the past most of the Secondary Filters on Diesels were around the 10 nominal micron level. That included CAT Diesel Engines.

I can't remember the details of the article but CAT did some research and decided to create their 2 Micron filter. Notice I did not say they invented 1 micron filters. Anyway CAT decided it was worth while to filter down that level.

On the Mercedes if you install the CAT filter CAT 1R-0750 as in my thread it is not a water separator but the filter itself is at least quart sized. You would have to take on near that quart of Water for liquid water to get into your Fuel System.

This is from my notes:
but CAT changed their rating standard. “Advance Efficiency” 1R-0750 became a 5 micron filter. The "Ultra High Efficiency" line of filters has a value lower than 4 microns filter or the so called 2 micron filter. See on page 11 of the CAT .pdf doc published in 2013 attached or a direct
link.. https://caterpillar.scene7.com/is/content/Caterpillar/C10467200


The abrasives in the fuel can over time wear down injection components and replacements will be needed. Both the Baldwin and CAT filters are rated at 2 microns. According to the Baldwin Rep, the BF7591-D has an efficiency rating of 91.95% for less than 2 microns. The CAT 1R-0750 has an efficiency rating of 98% at 2 microns. The stock filter is rated at 10 microns nominal. Meaning 50% efficiency rating at 10 microns. CAT did a study and using a 2 micron filter increase life of fuel injection parts by 7 fold compared to using a 10 micron filter (again is stock)."