Toto, the concern about the combo valve is very warranted because it's not just coming from schlubs like me, it's come from engineers and experts in the filter industry who don't fully trust it. And the concern is coming, in some cases, from engineers within the companies implementing them. I think Sayjac knows what I mean if he talked to the same guy I did.
Wix isn't the only one with a combo valve. It might be fine (now or at some later point) but when a guy who designs filters for a living tells me off the record that he has tested them and doesn't trust them, I take notice. Until I see a track record laid down, for me, it's "trust but verify." I'll let you do the R&D for me, even though I think this will be a feature mostly in low cost, "price point" filters which aren't my bag.
What concerns me about a "rubber" bypass valve is the changes that come from heat aging. In that regard, I would trust a silicone valve more than nitrile. A metal spring type valve, IMO, is a lot less subject to changes in operation over time than a soft valve. I can't think of any reason why it's "better" operationally than more conventional metal or metal/plastic valves, but I see it could be a great manufacturing cost saver for the mfr. and that's what would make it appear on lower cost filters to increase the profit margin.
I acknowledge that it's certain Wix, and others, have tested this setup and found it "adequate." The way I see it people can't jump on other mfrs. for design issues deemed by them to be also "adequate" (like endcaps, bypass valve designs, bypass location, etc.) and not be highly suspicious by this obviously cost-saving design. Those that can ignore this and other the other stuff are more into brand names (e.g. Brand name uber alles) and justify the technology according to their favorite and condemn the technology of their least favorite, rather than being objective about the different approaches to technology.
