Full disclosure: Amsoil ATL is not approved by Toyota for use in the Prius; this is strictly an Amsoil recommendation. Previously, Amsoil did not recommend using ATL in the Prius transmissions at all. See the correspondence from Amsoil:
The Low Viscosity Synthetic ATF has a "more information" link under APPLICATIONS it states that it is recommended for Toyota WS, but just below that it states that: *Not for use with CVT or Ford Type F applications. The Prius has a CVT(ECVT) transmission. There are *'s next to Normal Service and Severe Service below that; or is this left over from their prior recommendations?
The website does not have the most updated info. I was going off the info given to me by their tech line. iPhone ?
And why would you use the Amsoil product when the Toyota product was manufactured specifically for the application? The Transmission has no history of early failure and no fluid issues. I'm always surprised at the willingness of car owners to use products not approved by manufacturers when a specific product is available and has a history of success. Transmissions being at or near the top of the list.
In the Tundra transmission, the ATL seemed to perform a bit better per the UOA posted on BITOG. Regardless, I am not advocating that one should ATL, but rather, I was just relaying the info.