I'm going to jump in here and help several of you understand why this debate is either meaningful, or meaningless, depending upon your POV.
There are many factors to discuss which affect wear control when it comes to lubricated systems. In this case, we're speaking of engines ...
- air filtration
- oil filtration
- OCI duration
- oil type (grade and add-pack)
You all are arguing about only one aspect (oil filters) and ignoring the effects the others have. You have to be much more specific when you discuss any of these things, as they all have jobs to play in a very meaningful manner.
If you're going to run long OCIs, then certainly the capacity of the oil filter matters greatly. But in short OCIs, it does not. Obviously because there just isn't enough particulate in the system to push the filter to a point of concern in being overloaded.
Further, if you're going to run short OCIs, then efficiency does not matter greatly. Here's why ...
There are three main contributors to wear when it comes to particulate; silica, soot and metals.
When it comes to silica, that is the air filter's job to reduce the loading of particulate in the engine. The air filter has been referred to often as the most important wear control filter; a few studies (IIRC done by Donaldson, and perhaps Cummins?) show that clean air is very paramount to a low wear rate. Poor air filtration will accelerate engine wear greatly, no matter how well you filter the oil. That's because the air goes into the combustion chamber before it ever reaches the oil system; it does its damage early.
Another concern to wear related to ICE engines burning the fuel is soot; a carbon based particle of small size as a result of incomplete hydrocarbon combustion. How small? Well, generally soot starts out sub-micronic in size. Several SAE studies have shown that soot starts out in the single digits of a nm (nanometer). A nm is 100x smaller than a micron (micrometer). So let us say that soot starts out at approximately 4nm. It would have to "grow" (amalgamate) about 100x larger just to become 4um. Most folks understand that stuff smaller than 5um is difficult for any FF filter to catch; and certainly won't be caught with any great efficiency no matter how well rated the filter is. Only BP filters can hope to be reasonably efficient at that level. Further, because stuff smaller than 5um is mostly harness (too small to do much damage in the engine), the stuff that's this small just isn't of great concern. What controls soot at these nm and small um levels? The DI part of the oil add pack! Good amalgamation inhibitors reduce the growth rate of the soot size. So if your OCIs are not overly long, the soot never gets physically large enough to be in a range that filtration efficiency is in play here. This is a fact which many BITOGers don't take into account. Soot is controlled by two factors relating to the oil; one is the add-pack and one is the duration of use which affects the quantity of particulate present as a percentage of the sump.
As for the metals, only the hard metals (Cr, Fe, for example) can generally harm the engine. The soft metals (Pb, Cu) won't. And there's nothing that any air or oil filter can do to change the abrasive nature of hard metals. Oil filters can remove them from the stream (if of sufficient size), but oil filters cannot alter the actual nature of the hardness scale, one metal relative to another.
So, you have to take all things into context and discuss these as them being in concert, not in a vacuum.
It is not wrong to claim that a higher efficiency filter will trap more particulate; that's a decent generalization. But what is inappropriate to claim is that the oil filter will substantially reduce wear all the time; that is patently wrong. The oil filter can only trap what is present as a ratio of the overall sump, and only when the particulate is of the size range that the filter is effective in.
Do not confuse oil filter efficiency with effectiveness.
- if the air filter is doing a good job of reducing silica ingestion
- if the OCI is short enough that large quantities of soot are not present
- if the add-pack is sufficient that it continues to hold soot at a small enough size
- then the oil filter has very little work to do, and it's efficiency isn't going to affect wear rates in a tangible manner
Conversely, poor air filtration combined with long OCIs and poor quality oil will leave a heaping load of problems for the oil filter to contend with, and here the conversation would certainly lend itself to high efficiency and high capacity being paramount in an oil filter.
I would ask that many of you stop to realize that discussions about wear control in an engine is a multi-faceted conversation, and to not get your panties all wadded up over arguments which focus on one aspect while ignoring other very important contributors to the topic of wear control.
