I'm using the Chevron Mercon V (actually it is a combo fluid - Dexron III, Mercon and Mercon V).
It is a synthetic blend.
It is working very well in my 4R70W Ford transmission.
I have no analysis or other "hard" proof.
I don't think you can go wrong with Chevron oils.
Isn't ISO-Syn just Chevron marketing department's trade name for high quality base stock oils?
Anyway, ATF is probably the most heavily additized, processed, modified product we use. It's the farthest away from the dinosaur....
I've used Chevron's industrial lubes for over 30 years and never been let down. One time they identified that they'd sold us some mis-labeled turbine oil--right label, wrong blend, and this was a product that they don't stock but blend to order. They came to us, let us know, pumped out all the mixture from our storage tank and replaced it to the original quantity--probably two tank trucks. I've been well satisfied with Chevron products and recently bought a case of their ISO-Syn ATF for a transmission flush.
My understanding is that ISOSYN is group II+. Last I heard Chevron used Group III in the Supreme Synthetic ATF HD, with the ISOSYN in The Regular Supreme ATF Dexron III/Mercon. I sell lots of it to Nissan and others. Have yet to see anyone be able to oxidize it, but I've only carried it for 2 years. I have it in my wife's BMW, but she never leaves the city. I have the ATF+3 in my Grand Cherokee, and can't seem to destroy it even with the 100% mountain driving.
According to Kramer, et. al., "The Evolution of Base Oil Technology," (paper by three Chevron people, one engineer and two manager's) they intimated that the ISO-SYN technology is the modernized hydroisomerization process that yields Group III base stocks. Maybe someone from Chevron would like to clarify.
It won't compare to Mobil 1? I don't know about that. Maybe if you live in Northern Alaska or the middle of the desert. It's another one of those hot and cold issues.
I cannot speak for AMOCO, but I can speak for Pennzoil. I would stack our product up with the Chevron anyday of the week. Our's is not Group III, it is Group II+ base stock with a very robust additive package. Pennzoil ATF was the first ATF to stop the GM shudder problem. GM is using our ATF as a comparision to delvelope their next generation of ATF'S. I have Ford, GM, Chrysler, Mercedes Benz, BMW, VW, Nissan, Toyota, Audi, SAAB, Volvo, Honda, Mazda, and other dealers using our approved ATF'S for years without any trouble. I also have several transit systems using it in their Allison transmissions in their busses. It also meets TO-4 specs and works well in these applications.
So is the Pennzoil ATF better than Chevron ATF, don't know. But I do know it is as good as the Chevron. If your using the Chevron ATF, stick with it, I will stick with mine. (Unless Chevron buys Shell, Pennzoil-Quaker State)