Originally Posted By: NeilC
If a fluid is best for similar transmissions with a dip stick, what would make it unacceptable for the sealed transmissions?
For what it's worth, my 2010 Corolla has the same "lifetime" fill of WS, but it also came with a transmission dipstick, pan drain plug, and a real filter (not screen). Servicing it is as straightforward as can be.
Originally Posted By: NeilC
I haven't been able to find any significant reason why the Toyota transmission needs a special fluid to function other than Toyota says it does.
That's the real question. Besides being thin on the viscosity side, is the add pack bog standard or has some real chemistry magic to it? Until I get a good answer to that question, I'm sticking with OEM WS. More power to the experimenters, and I'm always will to consider other options, but since my transmission is so easy to service, it's no big deal for me to just drain and fill a couple quarts every oil change. If it was a real PITA, I probably would be looking hard at synthetic aftermarket options.