There are studies more relevant than this one due to time and technology. That's a 29 year old study. The Donaldson "total filtration" study is a tad newer, but comes to similar conclusions. More filtration is better.
The underlying question is "how much filtration is enough for normal use and how long do you need the equipment to last?"
Most any car made in the last two decades can EASILY run 250k miles with nothing special in terms of lubes or filters. Sealed systems along with much cleaner combustion make for far less contamination ingested and generated internally. There are of examples of vehicles running over 1 million miles with just normal oils and filters. Plenty of examples where cars go past 400k miles on normal filters. Routine maintenance shares the burden of the load of this. Also operating environment plays a big role; how dusty is it where you drive? Etc etc etc ...
Many of the older studies use a baseline established at 98% at 40um, or 50um, etc. The issue is that such a low baseline gives a very low standard to pass, and so any improvement seems massive. But today we can walk into any WM and get a decent filter that's 90% or 95% or greater at 20um. As Zee said, a filter that's 98% at 20um is probably 50% at 5um -7um. That means we can get regular over-the-counter filters which are far better than much of the "baseline" filters used in these older studies. So you're not going to see a huge reduction in wear as those older studies would suggest because you're already operating under conditions which are far, far better than decades ago.
There is no study I know of that anyone has brought forward which addresses lube filtration as a matter of a practical limit needed. Cleaner running engines, better quality lubes, much better "normal" filters all make this kind of a moot point. The normal variation of daily wear exceeds the ability to discern minor nuances in filtration. No one has a filter study done that proves I am wrong. Show me a study done in the last 5 years which uses current engines, lubes and filters, and then proves a real-world conclusion to be valid (not a HALT condition). I am not saying filters are worthless; that's not true. I'm saying that lube filters have a diminished role relative to overall wear control because air filtration and lube capability have improved so greatly they've put lube filters into the back seat. Once a lube filter is "good enough" it's not really a major player any longer. It helps, but it does not control. Lube filtration past a decent point (say 80% at 20um) is not the controlling variable as much as the other things. Show me a relevant study done recently using the current products available in real world use and then I'll pay attention.
