Ideally with any filter system you want to first filter to a small particle size, then filter to a very small size, that uses both filters and extends their life, for example most water
makers have two filters, a 20 micron and a secondary 5 micron.
I can’t prove it as I don’t know exactly where, but I have read that it’s against Yanmar’s recommendation to run finer than a 30 micron in the primary filter, reason given was excessive vacuum required to pull fuel through.
I assume those that run finer get away with it because the Racor
500’s most of us use are capable of flowing far more fuel than we use.
I have not been able to find definitively what the rating of the Yanmar is, but think it’s in the 6 or 8 range, not 2 microns.
However it’s funny
how many that will run 2 micron filters, won’t consider using non Yanmar oil
However it’s been said and it’s true, fuel can’t be too clean, so if you want to run 2 micron go ahead, but I doubt it’s accomplishing anything, and don’t do it to not change the secondary, filters over time will break down and the media come apart, you certainly don’t want that going into your injection pump