The average porosity of aviation oil filter media is about 40 microns. There are smaller and larger pores in the media but, on

average, the media will catch most of the 40 micron or larger particles. The smaller the particles in the oil, the fewer will be

caught by a given media. For example, a 40 micron media may only stop 80% of 30 micron particles, 40% of 20 micron

particles, and 10% of 5 micron particles. Steel particles in the oil are often five microns or less, so most will pass through

the filter media and circulate, hour after hour, through the engine with the oil.

Some of the race guys and I think all the big diesels use a secondary oil filter for ultra fine particle capture.  Perhaps others already know much more about this subject but it appears that installing a small-micron oil filter as a secondary unit fed by a secondary supply source could capture junk that our primary filters are not designed to capture.  This leaves the primary circuit intact including bypass, over-pressure relief and so on.   One article spoke about using the existing oil pressure transmission line as the source of oil to a secondary filter and directing the output to the oil pan, rocker cover or possibly the oil filler tube.    Even at the smaller line size for this smaller filter, the oil would be passed through at least once a few times each hour, says the calculation.    Searching reveals a number of fine micron filters (cleanable and replaceable) that are available in stainless and anodized high pressure cannisters that would easily fit on a firewall and apparently can capture debris in the 2-10 micron range.  Prices are all over the map.

It sounds like it could be done for a reasonable price plus hoses and connection fittings if someone thought it was worth testing.

Paul

IO550