I like this info. I have left over Mobil 1 ATF from my previous car. I will go ahead and use it in my Corolla in the next ATF change (drain and refill I do every 30000 miles).

This is very interesting. My understanding is that T-IV = Mobil 3309 ATF. And I was same understanding that Mobil 1 ATF was NOT a suitable substitute. Has this all changed ????

T-III is Toyota's equivalent spec for DexronIII. Don't let anyone tell you its different.
T-IV added HFM smooth shifts, timing and slip control, and longer life additive package to the Dexron III spec. I've seen a bunch of dealers blindly use T-IV in place of DexronIII with no apparent ill effects. If anything, the transmission shifts better.

Since you can use Dexron III, just about any newer ATF can be used.

If you want to know if a fluid is marginal, just look at the UOAs. I don't think that there are ANY outstanding OEM ATF UOAs from ANY automaker. Not every transmission hits 200k with no problems. For eveyone vehicle that does, I'll find an owner with the same that smoked the tranny before 30k.

If money isn't an issue, use any of the full synthetic ATFs. Mobil1 and RoyalPurple are easy store finds these days. Redline D4, Amsoil ATF/ATD,.... and others can be found online easy enough. Dexron VI is al$o a choice.

If you want a cost effective upgrade to the DexronIII, any Mercon-V or other blended synth multivehicle ATF can be used.

Since DexronIII/Mercon licensing has expired and isn't tested/police'd by Ford/Gm anymore, some members are wrongly created 'fear' against the new equivalents. If you do use a cheap Dex/Merc equivalent, stick with one of the name brand fluids. Another option is the TES-389 certified fluids, which mimics the DexronIII-H/Mercon specs.

Adjust your ATF OCI based on transmisison family history, driving style, fluid chosen, upgrades performed, and flush type at your intervals.

Castrol import ATF works fine in our cars, i had it in my car for 30,000 miles and never felt any weird vibrations or heard any noises and actually kept the transmission a little cooler than the stock oil because its slightly thicker and soaks away heat better when using a transmission oil cooler.
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only one ive used it in was the 2006 Toyota Corolla S i have right now and i had it in there for 30,000 miles before i went and got my 60,000 mile transmission system flush. but i loved it when i had it and didnt seem that much different than the original T-IV i had in when i got the car before i had to change the stock oil out at 30,000 miles. the temperature of the transmission oil seemed to be a little bit lower when i put the Castrol in than the stock fluid though which means it helps promote heat dissipation through the transmission pan better than the stock fluid.

http://www.9thgencorolla.com/forum/showthread.php?t=84143

We'll hear reports in the next few years that toyota transmissions blowing up, people blame it on Toyota. when in fact they used Dex 3 instead of toyota T-IV

I believe T-IV is rebadged Mobil type JWS-3309. Volvo shares some AW trannies with toyota, same AT, same fluid, different label. 3309 is a non-syn fluid per discussions with volvo gurus. NOT the same chemistry as the multi-vehicle ATFs, and is designed to handle the partial-engagement behavior of the torque converter, an operation that was developed much later than the release of Dex III.

T-IV added HFM smooth shifts, timing and slip control, and longer life additive package to the Dexron III spec.