My understanding with atf synthitic for newer model 2006+ is not recommend as I read it here somewhere. Someone tried atf synth and had issue.
Can anyone confirm using synth atf with zero issue in 2007 lx tranny?
I've not read that. Would like to see what they used, at what miles and history of vehicle!
I do know of some concerns with switching form conventional oils to synthetic oils.
The concern with switching to synthetic (transmission):
1st; It clean seals and if those seal are bad (dry & cracked) or leak is plugged by gunk, they will start leaking once cleaned. (same with engine)
2nd; Gunk starts moving, plugging & fouling pressure & flow of ATF.
3rd; Fiction plates may be held together with gunk, clean and they may fall apart.
If 1st & 2nd are of a concern, then drain & fill ~3qt at a time over time is safest bet.
If 3rd is concern, well it's a bad transmission.
I use nothing but synthetic lubes when & where I can, it just a better lubricant period. The concern I have with using anything but Toyota WS is compatibility.