I was thinking about why my OEM Toyota filters, which are not designed to be used for crazy long OCI of 10K+ miles, have poorer filtering efficiency for smaller particles than the filters used for 15-20K intervals.
I'm clearly no oil expert, so please go easy on me if my theory is completely out of whack. LOL
The motor oil itself can suspend quite a large volume of particles without those particles damaging parts as long as they are below a certain size. My OEM filter can remove those larger particles and ignore the smaller ones, as long as the oil is never left too long to be fully loaded beyond its limit with smaller particles. If the oil is changed soon enough, those tiny particles never accumulated enough to cause engine harm, beyond just normal wear and tear.
If the oil is allowed to accumulate too many small particles, beyond what it can keep suspended, then they may increase engine wear.
For doing long OCI, the filter must take up some of the duty of keeping those small particles from loading the oil too soon before the oil change. Thus, the extended OCI filters having a much higher efficiency on smaller particles compared to cheaper/normal oil filters.
Would this explain why so many people who used the cheapest or average oil filters, along with normal/cheap oil, but doing so at shorter change intervals, can have engines that last 500K+ miles without any major rebuild of parts that would tend to wear out?
Then, would it also be right to say that for normal OCI, within OEM specs, one wouldn't be gaining any extra engine protection by using a high efficiency oil filter? Maybe even less protection if the flow rate and bypass specs are too far off from OEM spec on OEM filters?
My Toyota Denso-made oil filters I now use on 2 rigs, are considered to some of the "worst" in terms of micro efficiency, yet we all know, Toyota doesn't mess around when it comes to making their engines run for a long time. Did the engineers understand that filter efficiency below a certain threshold, using non-extended OCI, is a worthwhile tradeoff in order to have a filter that is less likely to go into bypass mode?
Please, let me know how wrong I am, which is probably all of it. But, I have been reading BITOG for years now, and this seems to be the general way these things work, right?