Originally Posted By: another Todd
ZeeOSix---That is an interesting point, but I still think having the inlet and outlet (bypass) close together rather than opposite ends, will work better as the bypassing oil does not flow sideways across the media(possibly dislodging contaminates on the way) in route to the bypass.
IMO, the location of the bypass valve inside the filer is more important during an initial cold start-up than it would be after oil flow is fully established through the media.
If there if established oil flow through the media, and if the bypass valve opens, any trapped debris should remain trapped up against the media because the oil flow force will hold it in the pleats and prevent it from moving around.
Reason that the bypass location is more important during an initial cold start is because when the engine is off and if any debris has sluffed off the media, it will collect at the low point of the filter. In the example of my Toyota Tacoma V6, that would mean debris could end up at the base of the filter (since it's mounted base down), which means a base end bypass valve would be more likely to sweep that debris into the engine than a dome end bypass valve.
Ford (Motorcraft) filters have a base end bypass valve because almost every Ford engine has the base of the filter pointing up to some degree when the filter is mounted.