0.1µ is an excellent micron rating. Our Clariflow membrane filters (we have also used Pall), filter the wine on the final moment before going into the bottle filler at 0.45µ We consider it a "Sterile" filter, and as such is steam autoclaved for 20 minutes before being mounted in a steamed stainless steel filter housing. Now I know soot is very small and if hard can cause abrasion and metal polish. But, I have also seen a chart on the wear factor of engines from 10µ on down to 1µ and it is an interesting graph. Above those numbers, in the 15-30µ range you see the graph of engine wear climbing, but at 10 and lower it does decline, but at a VERY small amount, IN PROPORTION, I might add to that which was 15µ and above. Bacteria is 2µ . And, just 1 micron is equivalent to 0.000039" dia size. That is referred to 39 Millionths of an inch.
Now somewhere in there around 3 microns the graph is moving so slowly down, in terms of engine wear, that you have to wonder about how much you really are preventing wear. If you save 2% wear on the engine from going from 3 micron to 1 or 0.1 micron are you really needing that extra 2% (or whatever it might be in terms of engine wear reduction) for the life of your engine? Your underbelly rust from adverse road protection of ice in the winter may be more damaging to your vehicle and pocketbook than the minuscule little extra wear benefit of sub micron filtration.
Toilet paper is cheap, but I have also seen pictures of oil channeling in TP filtration. An oil channel does no filtration, and therefore is taking away from the conceptual and mechanical advantages of small particle filtration that you started with. I have seen in other forums PC counts of filtrations, of normal full flow oil filters. Go to this thread:
http://theoildrop.server101.com/forums/showflat.php?Cat=0&Number=727892 and check out the particle count of the Purolator full flow in the greater than 2µ range. Only 782 from 2 to 5µ. Folks, that's not very many!
The real trick is slowing oil down through a decent filter system, and allowing the depth filter to do it's job. Bypass filtration, in any choice of flavors (brands) can do that and whether it is 2 micron, 3 micron or 0.1 micron is not as important as constant steady flow rate in the 1/2 gal or less per minute range.
One other thing to consider in 3,000 vs 10,000 mile OCI between TP and spin on, is every 3,000 miles you are basically loosing 1 quart (more or less) of oil. If it's synthetic, like GC, Amsoil, Mobil 1, etc don't forget to take that into your total final equations.
Just some food for thought this weekend.
BTW, to Col.
Welcome.. I hope you find our candor and varied views enlightening.
Now that ain't too shaby!! And they have great nominal micron ratings as well.
No, wait a minute. That is what I would be thinking if I actually believed the non-factual, non-experience based, imagination-induced ramblings of certain posters above. Now that I have my wits about me I am virtually certain I am using and have actually experieneedd and documented the facts I presented. I guess facts and reality just don't matter once a mind in made up. 
