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...Is there any data to support that? Just curious. I know there are lots of people complaining about combo valves I'm just interested in proof that these valves are inferior. I'm sure there are thousands (maybe hundreds of thousands or more) of combo valve filters out there.
I don't have proof nor necessarily believe that combo valves "leak". What I do know is that nitrile adbvs eventually lose their pliability, I think generally ~5-6k miles is considered useful/functional life. When it just controls drain back, not huge deal. Worst might be seen or heard, a start up rattle. Hardly a major engine issue, annoyance more than anything. Otoh, when it also controls bypass psi, could be something greater involved.
One other thing to consider. When GM dropped block bypass and went filter integral bypass, easiest move would have been to use a combo valve already used in other ecore filters. However, on it's ACDelco GM ecore filters with filter bypass, they use a traditional poppet type dome bypass. No combo valve. One can draw their conclusion(s) why that is.