I replaced my 2008 Toyota Matrix cabin air filter recently and it was more vexing than I could have imagined. The OEM filter from Toyota has an arrow printed on it that points UPWARD. The aftermarket replacement filter from GKI (part #CF1040) has an arrow pointing DOWNWARD. Of course why would they make it easy for the consumer?
I contacted GKI and they recommend pointing the arrow upwards, even though after verifying the airflow in the duct, it's definitely flowing down. Is this a Toyota thing, does airflow not matter, is GKI clueless?
If the filter has the words "AIR FLOW" printed on it, then the arrow shows direction the air should flow through it. If it is stamped with UP, TOP, or nothing, then the arrow indicates installation direction.
Every cabin filter I have replaced, the arrow points upward.
Every after market cabin filter I have replaced has the arrow pointing DOWN. You'll have to do some research on this.
I've done WAY too much Googling on this and gotten nowhere. As far as I can tell, the arrow printed on the filter housing is intended to show the direction of the airflow. And that's what's confusing with the Toyota filter, I tested the airflow, and it definitely it blows downward. That said, why would Toyota's filter have an arrow pointing upward? It just doesn't make sense, unless it's done to force me to buy Toyota filters which cost 3 times as much as the aftermarket ones. Thanks Toyota!