This seems to really come down to preference. I just did a BUNCH of research on this and decided to go with Amsoil. I have seen some data measuring the amount of impurities after use and Amsoil came out on top on a few samples I've seen. Then again, I've seen others where other brands like Royal Purple or Mobil 1 came out on top. Downside is price at about $16/qt for Amsoil, but this wasn't far off from about $14/qt for OEM Toyota ATF. IMHO, any reputable brand is prob good.