Well, this is the first I've heard of someone wanting to try this in particular!
IDK! Although, if the '96 Lexus uses DexronIII/Mercon and not T-IV, who knows! My sisters '98 Camry V6 is essentially the same as the ES-300 and uses DexIII/Merc
It's a gamble but, I don't see why it would hurt. "If" T-IV is backward compatible with that tranny then maybe the friction modified Matic-K may not change the shifting pattern either.
Just out of curiosity, I always wanted to try a full D&F or two of Chyrsler ATF-4 in my wifes Lexus RX instead of the T-IV. I haven't yet!
Yeah, Char Baby, it calls for DexIII, and I think I've read that the Matic-K was proprietary but very near the DexIII(H) spec. It only drains 2.5 quarts, so I think I'll try it. I'll report back after I have a chance to drive it.
Wow, I haven't seen the(I beleive it was actually called Dexron II "H") spec in years as it was only out on the market for a short time before DEXRON III/Mercon hit the shelves.
I believe the order of DEX ATF's were, (and I could be wrong on some of these):
Dexron
Dexron II
Dexron II "D" ???(Never seen this one, only heard it existed!)
Dexron II "E"
Dexron II "H"
Dexron III(IDK if it was always called DexIII/Merc)
Dexron III/Mercon
Dexron IV(I've never seen DexIV, only heard it existed!)
Dexron V ?(I think the "V" was skipped over?)
Dexron VI(current Dex ATF)
But anyyyywaaayyy! I think you'll be just fine.
My sisters '98 Camry V6 auto tranny also only held ~ 2.5 qts on a drain/refill so, we did it about every year. Sold in '11 and everything was running fine using Wal*Mart SuperTech DexIII/Merc since '01.