A little off topic but it fits with the micron filtering topic so I will toss this out for folks to consider.
I was at a repair facility for my poles saw and decided to ask for a filter for my 3400 HydroGear drive for my zero turn mower. The manager and I got to talking and I told him I had ordered some filters online for about 1/3 less than his selling price of $18 each but they wouldn't be in for several days. He said I hope you got the OEM filters from HydroGear and I said they were.
He said one customer decided to go to the auto parts and buy a filter "that fit" for his mower and got a 10 micron filter thinking it would be ok. Well the filters are suction filters on these machines and while the 10 microns filter great the resistance is too great and starved his pump for oil resulting in a burned up mower transmission. The OEM filters are 20 microns (according to the repair shop guy) filtering a 10W-50 motor oil and anything less than that causes too much restriction in the oil flow. I did end up buying 2 filters so I could get finished with my oil change. Now I have 4 filters which should last me for 600 hours of mowing (including the 2 I just installed) @ about 75 hours per year, I think I am good for a lot of years.
As a point of interest also he recommended 15W-50 full synthetic rather than the standard OEM required 10W-50 high detergent motor oil. He said it would quieten the HST whine down a lot. OF COURSE, no one carries that grade of synthetic (besides him) that I could find so I put back the regular dino oil this time.
A little whine over the motor noise isn't that bad.