I agree that soot and silicon are the two most damaging issues in oil. The wear metals are much more the result of damage, rather than the cause of damage. In a UOA, we get to see not only the effects of wear (Al, Cu, Fe, Pb, etc) but the causes (soot/insoluble levels and silicon count).
Like I said, I can't put pure numbers to the equations I profess. Not that it cannot be done; with enough time, money and accumulated mileage, we could all study the effects of our individual beliefs. But I, for one, do not have unlimited time and money and resources, so I have to lean upon some conceptual logic, and some anecdotal evidence.
Why do most engines not get used past 250k miles? Probably because too many things take the engine out of service before it was actually no longer fit for service. Vehicle crashes, rust corrosion of the host vehicle body, lack of care/interest from the owner, etc. It's not that engines can't last past that mark, it's more due to the fact that circumstances preclude their use past that point.
UOA wear metal results show us the materials that we can draw assumptions from. Low wear-metal particle presence in a UOA means we can presume low wear. While possible that some huge chunk above 5um is floating around, that is indicative of some catastrophic event, and not "normal" wear. Further, big metal chunks are caught soon by the full flow filter.
And the sump maturity level driven down by Gary shows my point to a very good level. It takes nearly 30 passes through the bypass filter to remove the bulk of the contaminants. And that is assuming an untrue condition; that being there is no new contamination. In reality, new contamination is being added all the time. What we don't know for sure is: at what rate, and in what size.
That's why I addressed the issue of soot. Soot starts out sub-micron, and stays below 5um via the effects of the oil additive package. So, until the oil becomes overwhelmed, the BP filter is only assisting the oil's ability to do work, by lengthening its longevity.
The BP filter is not reducing wear, because filters don't affect metal, they affect oil. Only lubricants can reduce wear. It's a fundamental relationship that has to be understood for the simplistic "aha" moment it demands.
Q: Can any filter, no matter how efficient, make an engine wear less, or more, of it's own accord?
A: Absolutely not.
Think I'm wrong? Try running your engine with a super-premium bypass filter, WITH NO OIL IN THE ENGINE. That filter has ZERO effect on the engine. In fact, that could also be turned the other way and asked of the full flow filter as well. If you could complete the oil circuit, and remove the media from the full flow, with no bypass filter installed, would the engine grind to a halt immediately upon the loss of the media? Certainly not! The affect filters have is on the OIL. The lubricant is what reduces wear on any piece of equipment. Bypass filters cannot reduce wear in an engine; they can only prolong the ability of the lubricant to do its job. The effect of a filter on oil is a direct relationship. The effect of oil on the equipment is a direct relationship. But the effect of filters on equipment is an IN-direct relationship. It doesn't matter if you're talking full flow or bypass filters.
Think this sounds extreme? Consider to opposing thoughts.
Would you run an engine with oil, but no filter? (sure, lots of engines are done this way. Small air, and even some liquid, cooled engines use this type system).
Would you run an engine with a great filter, but no oil? (Ummm, nope. Can't think of one engine design I know of that would sustain this for very long at all. Can you?)
So the key to the whole oil vs. filter concept is that lubes help the engine, and filters help the lube. Filters do NOTHING for the engine.
The concept of bypass filters is often only looked at from one viewpoint, but it's often skewed. We take for granted that full flow filters do a decent job on their own. Again, consider the whole concept, but with a different twist. Consider the use of a full flow filter that was as efficient as our concept of a bypass filter. Now THAT would be awesome! Full flow, 99.9% pure oil! Practical limits on size and cost prohibit such endeavors, but conceptually it's possible. So, in reality, bypass filters are nothing special; they are only "extra fine" filters. If you removed the full flow media, but left the bypass filter installed, I doubt you'd have as good results as what we consider "normal".
The true viewpoint to understand is that filters, regardless of their name or design, only serve to lengthen the life of the lubricant. But they also should only get credit for this, when the oil is too tired to do the job on its own. Bypass filters, in our traditional sense, only are truly effective after the point at which "normal, conventional" oil/filters start to fatigue. So, once again, I pound the gong; if you change your "normal" oil and filters often enough, they have the same effect as "bypass" filtration.
Time for another analogy:
We need to get a 100 pound load over 10 miles of mountains. The goal is to trek the load of 100 pounds 10 miles, (because “work” is defined as force multiplied by distance). We cannot do the work with one hiker, as he would fatigue and eventually fail; we’ll say a “normal” person can go 2 miles with 100 pounds before failure. So we have two options. We could add another hiker, and split the load. By dividing the load in half, perhaps the ability of each hiker is multiplied 5x. Why 5x? The exertion level is not a linear relationship to the load! However, if we didn’t want two hikers at a time, we could also substitute a new hiker, swapping in a fresh hiker every 2 miles. The end result is that the 100 pounds went the 10 miles; the work goal was met. It’s just a question of how it got there. Did the original hiker get assistance, or did he get replaced? See the point? Do you replace “conventional” oil/filters often enough to sustain low wear, or do you assist the system with “better” filtration. Same result; different methods. Bypass filtration is not about result manipulation, it’s about process manipulation.
So, let’s get back on topic. If bypass filters can only effect oil, then it's fair to reason, (because of anecdotal evidence such as UOAs and 1-million mile vehicles), that if you change your oil often enough, the lube system does not need the help of the bypass filter.
Now, you can't have this debate without having some acknowledgement of the practicality of bypass filtration. Clearly, one can make an engine last 1 million miles with "normal" oil and filters; at least two examples exist. So, if those guys would have used bypass filters, would the engines go two million miles with bypass, but would have failed at 1.5 million miles without? I can't say. It’s hard to define a practical limit on such extreme operation.
The pragmatism of the whole debate comes into play when we try to assess "needs" versus "wants". Clearly, bypass filters are not "needed" for equipment longevity; too much evidence to refute that. The question becomes, at what threshold do you "want" a bypass filter? Now, you've entered the concept of "value". Value is based upon many individual parameters that can be rank ordered, in differing priorities, depending upon each person's perception.
1) expected length of ownership
2) expected desire for resale value, if applicable
3) expected operating environment
4) expected operating severity
5) tolerance for initial purchase costs
6) tolerance of initial installation efforts
7) tolerance for required maintenance costs
8) tolerance of required maintenance efforts
9) availability of maintenance components
and so on ...
Here are the three concepts that allude most people:
1 Filters don't make equipment last longer; they make fluids last longer.
2 Bypass filters are clearly not a necessity to achieve equipment longevity.
3 ROI is the true measuring stick by which the preceding two points should be judged.
