I am in the process of changing my old fully synthetic multi-vehicle ATF to the specific fluid my cars call for. Either DEX III, Toyota T-IV or Toyota WS. So far I have gotten to approx 90% of the vehicle specific ATF in the 4Runner and the LS400. In other words, the 4Runner has approx 90% Toyota brand Dexron III (3 drain an refills of 5.5 qts) and the LS400 has approx 90% T-IV (5 drain and refills of 3.5 qts). I drive the same roads everyday. I don't know if some of what I say is good or bad. Here are my observations. One is without question and the other does have some subjectivity to it. First, when I leave my house first thing in the morning in my LS400, I merely coast down the hill from my house. For the last 24 years the Tranny would stay in a lower gear until I got 2/3 of the way down the hill before it would shift up into a higher gear. Note I am just coasting, no throttle what so ever. The engine would rev higher as it coasted staying in a lower gear until about 2/3 way down when it would shift up and engine RPM's would go down. After changing to the T-IV it no longer does that. It goes to a higher gear almost immediately as I go down the hill. This is very interesting. Second, when I drive my 4Runner the 30 trip to work up and down the hills I observe it shifts sooner into a lower gear as I climb the hills. Before with the fully synthetic mulit-vehicle ATF the transmission would stay in the higher gear longer and was more apt make a dramatic downshift when it shifted. Almost like it dropped down 2 gears or it just stayed in the high gear a lot longer before it shifted down. I haven't changed the ATF in the newer cars in my fleet yet. Remember, both the 4Runner and LS400 have a bunch of miles on them. I have no credentials in mechanics and am making an observation that you all can say I'm crazy or and idiot or merely mentally incompetent. It appears with the multi-vehicle fully synthetic ATF I have been using for years worked fine in my cars. Look at the miles on my older stuff. Obviously my transmissions have been taken care of as I always change the fluid. I even have the scan gauge to check the ATF temp in my new stuff to make sure the levels are correct. Here is what I think. I believe the ATF I was using "hung on" longer than the OEM Toyota fluid. It didn't shift as often as the OEM does. Going down the hill in front of my house it "hung on" in a lower gear longer before it shifted. Going up hills it "hung on" longer than the OEM does. It appears it reduced the shifts. Now that probably is a good thing???? But from my point of view, the OEM produces a more smooth driving experience (At least on the 2 older vehicles) As I get to LS430 and GX 470 I'll update you. It may be a few weeks as I am going through some ATF.