That, my friend, is the million dollar question. I know of only two companies that post that information freely.
Motorcraft used to post it, but I checked recently and cannot find the information any longer. To their credit, they used to post it. But the numbers were nothing to write home about. One filter, for example, was only 80% efficient at particles 40 microns and larger. 40 microns!!! Thats friggin boulders inside the clearances of engines. Another thing revealing about their oil filters was that not every filter had the same rating, it was all across the board.
The only other company I am aware of that posts such information is Amsoil and all of their EaO filters are 98.7% efficient at 15 microns and as far as I know, based on the information I can find, is the best filtering ability available. I have not found another filter yet that posts such numbers. Their bypass filters are even more outstanding coming in at 98.7% efficient at 2 microns I believe it is.
With regards to filter construction I will add only this. Its one thing to compare a new filter to a new filter. Its quite another to see how that construction holds up after a few thousand miles.
I'll give you an example. I have a customer that had two vehicles that I serviced and bought a third. He ran an engine cleaner through the new used vehicle per a recommendation from me, for 1500 miles, using an off the shelf filter. He then wanted to me to come an service it from front to rear and service one of his other vehicles that was due having 10,000 miles on the oil change.
I brought my oil filter opener because I knew what to expect and what I would see, but I wanted him to see it to sorta re-enforce the quality of the products he was already using.
I cut open the 1500 mile filter, I dont recall what filter it was. It wasnt a Fram, he is dead set against those for any interval, but it was one of the cheaper brands.
At any rate, we cut open the 1500 mile filter to inspect it to see what the engine cleaner had removed if anything. Well, he was sitting right there with me when I did this and as I began to inspect the pleats, the thing just crumbled apart. Very little pressure caused the pleats to just disintegrate because they had become so stiff. I even gave him the element to see for himself. The drain back valve had lost a great deal of its pliability but probably still worked but I would not have left that filter on the vehicle much longer.
After that, we pulled in his other vehicle that had 10,000 miles on the oil. I proceeded to pull the filter (Amsoil), cut it open. I gave him the element and let him do the inspection. He was able to spread the pleats apart quite a bit to inspect in between them for any signs of trouble and the filter STILL held together. It demonstrated to him what I knew.
So again, comparing the construction of a new filter to a new filter may reveal a few things, but nothing like comparing them after they have been in service for an oil change interval.
