Here is a test of a bypass oil filter with a particle count, put on without changing the oil and the oil retested after only 200 miles using the tp filter.
https://www.frantzfilters.com/
There's nothing new with these style filters. Whether it's the Frantz TP filter or the older string-wrapped bobbin style, or the AMSOIl setup with a spin-on bypass element.
All the bypass filters can be shown to produce cleaner oil. None of them have been proven to provide longer engine life vs a newer high efficiency spin-on. That's the conundrum. As you go smaller in particle size, you get to a point where particle counts don't matter.
Consider this: on the fuel systems I engineer, the operating pressures are over 30,000 psi. The clearances are single digit microns in some locations. The precision and tolerance is mind-blowing in some parts of the system. And the surface loads in terms of PSI higher than anything else in the engine, blowing away rod bearings, pin joints, gear teeth, etc.
Yet even as we try to get fuel cleaner and cleaner, we've discovered that there is a critical particle size below which trying to remove it only shortens filter life and does nothing for hardware life. In fact, testing showed that when we tried to filter out 2 micron particles, all we did was plug filters with things like pipeline corrosion inhibitors and other trace fuel content that show up as semisolid particles. Letting these through has no harm on wear rates or durability.
So I relaxed the nominal media spec to 3 microns from 2 microns, cured almost all the premature plugging issues, gave our customers an average of 2x-3x filter life while having no detrimental effect at all on injector or pump life-- the field data actually suggests somehow that components are lasting a bit longer.
It turns out that there's a critical particle size somewhere around 4 microns that is where you transition from harmless to relevant in terms of wear mechanics. And this is in the fuel system where fuel is the lubricant and you have super high pressures.
The high pressure fuel pump is oil-lubricated on the bottom end and has roller followers on a camshaft that activate the plunger pump elements. The unit loading here is extraordinarily high--higher than any other oil-wetted surface in the engine. And higher than any oil-wetted surface in your typical passenger car engine.
Yet I have torn apart these pumps after 20k hours on petroleum 15w-40 with only 20 micron spin on filtration and there is so little wear that camshaft surface finish is still clearly discernible as being the way it was when brand new.
So if a cheap petroleum 15w-40 (shell rimula) is sufficient to keep an extraordinarily highly loaded camshaft pristine when used with mere 20 micron spin on filtration, I interpret this experience as strongly suggesting that nobody needs oil filtration much below 10 microns. High efficiency at 15-20 microns is far more important than having any efficiency at 5 microns.
As I wrap up this long post, I will suggest the ultra-clean oil might have one advantage in gasoline engines in terms of deposit prevention if you can filter out deposit precursors more effectively. But this is not a wear mitigation measure, just potentially an increase to engine life anyway. And by my lights, the PGI filter media that has performance of over 98% down to 15 microns is so good that there's no value whatsoever in trying to improve on this filtration performance if you are trying to optimize engine life.
Regular use of the PGI-made 10k mile filter will eliminate filter performance as a variable for engine life.
