My reference for the design spec for the oil filter is the BMW service documentation, also referenced in the owner's manual. BMW warrant the engine under the standard warranty, or the extended powertrain warranty, for up to 100,000 miles, if you follow their oil change recommendations. Some will say that a plugged oil filter at 15,000 miles will not show up in resultant engine damage until after that 100,000 miles has been accumulated, but that just seems a little absurd to me.
Oil filters are not all the same. Appearance means nothing. The same factory will produce multiple filters with different media types. Those different filter media last different time spans, have different capacities, and different filtering performance (in micron rating). Absolutely, every non-purging filter has a finite capacity, agreed.
I work in km myself, not miles, but I haven't seen the oil change interval from the service indicator shorten much from the 15,000 mile base point. It seems to go longer with more highway use, but not much shorter. Of course, BMW recommend that with extreme service conditions the oil change interval should be shorter, but I am working on standard driving conditions here.
The tax I was referring to is a non-existent environmental tax that would perhaps promote conversation. Just an idea
My eight times was tongue-in-cheek, but any design engineer uses a safety factor, and I think the Germans are more conservative than some. Your 15,000 miles to failure assumes no safety margin. That's just crazy
You know they have to be using something like a standard 1.5 factor just to reduce the probability of early engine failures. Changing the filter at 10,000 or 12,000 miles seems prudent. Changing it at 7,500 seems ultra-conservative. Changing it at 3,000 seems a little OTT.
Just my $0.02 Great discussion, beats many of the other standard topics here!