Used TOYOTA WS Automatic Tranny Fluid analysis :

[sbergman27]

Originally Posted by bronsin

Going to leave my factory stuff in for as long as I own it. Might change the filter every five years or thereabouts....

If you are not planning on changing the fluid, I'd suggest leaving the filter, as well. I would expect the filter to gain efficiency over time, if anything. If it clogs (doubtful), you'll know it. Otherwise, it should be fine. Changing the filter means you'll have to drain the fluid into a container, pull the pan, replace the filter, and then pour the fluid back in. All this entails chances for contamination. And the factory service manual specifically says *not* to do that. It says to *always* use fresh fluid.

-Steve