"B A R R Y" wrote in message
. net...
John Horner wrote:

This is way off the woodworking topic, but the function of an
anti-drainback valve is to keep the filter full after the engine is shut
down and oil pressure is no longer generated. It is normally a rubber
flap which acts as a one way valve.

I totally understand and agree. I've cut filters open to check 'em out.
We cut open every filter that comes off my airplane to inspect for metal,
so I have a purpose-made tool.

My filter is empty on this vehicle when I remove it, all 12 or so times
I've done it. Frank's is not. G

On some vehicles it does not matter if the filter oil drains back. Toyota
has a specific spec for this particular filter and vehicle that the OEM must
adhere to. Aftermarket tends to build fewer filters that work with many
more applications and will add features that are not necessary in order to
cut down on bigger inventories. Sometimes more features are cheaper to
produce than 3 or 4 of the same basic filter with 3 or 4 varying degrees of
protection built in side. Toyota's filter probably does not need the check
valve and is probably left out to assist with an easier and less messy
filter change. Franks filter probably adds .01% more protection during cold
start up after setting over night, maybe.