On the newer 100's they specify that you only have to top off the tranny fluid and it can't be drained and refilled. In addition the new fluid isn't compatible with other fluids.
What is it about this fluid that it never needs to be changed?
The world standard (WS) fluid, I believe, is synthetic. Whatever it is, the lifetime is like 100K mi (claim). You have to replace it w/ the same Toyota WS fluid. Older 100's used dextron II/III and type-IV fluids. Synthetics like Amsoil are T-IV compatible, but not WS-compatible. There's a sticky up on ATF. This is the main reason why I bought a '03...last year that T-IV was used and last year with the ATF dipstick, first year w/ the 5spd.
