x2 for the Valovline Maxlife ATF.
My Previa's auto trans was having with the overdrive. At freeway speeds a shudder would pass through the whole vehicle as if I'd run over a rumble strip when the trans shifted either in or out of overdrive. At first I just thought I'd hit a rumble strip; eventually I figured out it was the trans, since there were no rumble strips in sight and I began to pay attention to what else was going on when it happened.
No telling if the trans fluid had ever been changed in my van during its first 230k miles before I rescued it ... I really didn't want to swap the trans out so I pondered what my simple options were. I dropped the pan and drained out what I could (about half of the 7 or 8 qts) and replaced it with Maxlife. Imagine my delight to find that the rumble vanished! This made a believer of me.
Sometime soon I'll swap half the fluid again and be down to 25% old fluid.