Delfin, I'm curious, are you conducting oil analysis? Some evidence suggests that certain additives can be removed by extreme filtration. For anyone who does oil analysis, whether or not bypass filtration is used, I recommend taking a reference sample, that is analyzing a sample of new, unused oil, to which later samples are compared. If additives were being removed, the reference sample would allow you to identify this.
An excerpt from an article on the subject, "The lubricant supplier said that additive suppliers indicate using filters down to a 3-micron size in hydraulic fluid
and wind turbine gear oil applications should remove particulates without leading to additive removal. But use of filters below 3 microns can cause problems. The lubricant supplier says, “We often hear that defoamers may be the first
additive to be removed from a lubricant if filters that are less
than 3 microns are used in a specific system.”
Another article on the subject
https://www.machinerylubrication.com/Read/30566/defoamant-additives-filtered
Probably more of an issue with splash lubrication, as in gearboxes, but still worth monitoring in crankcase oils that are uber-filtered.
It seems defoamants are the most vulnerable to extreme filtration.
For those who are interested, an article on oil analysis
http://stevedmarineconsulting.com/wp-content/uploads/2014/03/FluidAnalysis143_Final.pdf