Originally Posted by 901Memphis
The differential pressure in the synthetic media filters will be lower than cellulose filters so it's not that crazy for the Ultra to have a lower bypass setting and still maintain full filtering without bypass during cold start.
Do you have data to back that up? All I've seen is a comparison chart done years ago on various cellulose-glass fiber blended semi-synthetic media oil filters, showing there was (and there can be today) a pretty good spread between even that one type of oil filter media.
I'd basically agree that the Fram Ultra, with its unique all-synthetic double layer media CAN be different on pressure drop. We don't know. MotorKing was a poster on here who could maybe tell us. Fram has been mostly mum on this whole GM-Mazda-Subaru bypass pressure valve setting issue. Its like they don't want to address it or something.
In the chart above, the "Ultraguard" I'm pretty sure is referring to an AC-Delco Ultraguard, not a Fram Ultra, so I think that used the typical blended glass-paper media like the others.
That chart does show there can (not always) be a different flow rate that pops the bypass valve.
Another factor is using an oversized oil filter, where one can physically do so. Some of us can. With an oversize one, the pressure drop should be even less, since the flow is spread out across more media area.
I'm almost concluding, without real proof I can't yet, that using an
oversize Fram Ultra oil filter should
equal using the lousy paper media AC-Delco oil filter, even though the Ultra has a minus 10 psi too low bypass threshold (13 vs. 23 psi). ...2018 Equinox 1.5L turbo engine, also covered by the notorious GM TSB about bypass valve settings.