The example I gave with warm oil at high rpm is only one example of a worst-case scenario for bypassing. With cold oil, engine rpm doesn't need to be nearly as high before bypassing occurs. The FRAM Extraguard for example would likely be bypassing a lot of oil continuously even at cold idle. The figures I came up with are also based on brand new filters with no dP increase from dirt loading.
Subaru engines don't get worn out prematurely even with aftermarket filters because a filter bypassing on a regular basis should normally only cause a very small increase in engine wear. However, in certain conditions, the bypassing might be problematic.
I agree and I think the FRAM Endurance will result in less engine wear than an OEM filter even when if the FRAM is bypassing often, but only in normal conditions when there isn't a lot of large abrasives in the oil. I've seen multiple teardowns of failed Subaru engines that were using cheap aftermarket filters, and most of the wear surfaces throughout engines had deep scoring from large bits of bearing material circulating through the engine. A bypassing filter will allow orders of magnitude more of these large bits to circulate, and it's the large stuff that causes most wear in these conditions, and when wear rates are already really high.
In this specific example, if the engine is going to be replaced with a new engine anyway instead of being rebuilt, I supose it doesn't really matter, but in some cases it might make the difference between replacing a failed engine component and replacing a long block.
The other concern I have with bypassing filters is clogging of oil screens and oil control valves. This is a common issue on Subarus and I suspect oil filter bypassing is a contributing factor. A filter that isn't bypassing will capture nearly 100% of any chunks of carbon large enough to clog an oil screen, whereas a bypassing filter will let a lot it through.
The risks of filter bypassing may be low, but they need to be weighed against the benefits of more efficient filtration, which are small. Car manufacturers seem to prioritize bypass resistance, but do not seem to prioritize filtration efficiency. This might be because normal abrasive wear will never cause issues within the warranty period, whereas a bypassing filter could cause warranty claims or make the fix more expensive.
All that said, I have an OG FRAM Ultra on my shelf that I will be using on my WRX, but I feel that if there's a filter like the Purolator available that won't bypass and isn't much less efficient, it's a better option. If I had a naturally aspirated Subaru like yours, I might be inclined to use a FRAM Endurance, as it shouldn't be bypassing all that often.
