This topic has been discussed a lot, but after reading a dozen threads, I still can't decide which fluid. (I've decided the process, however, which I'll mention as review below.)
Which fluid is the BEST to use? I'm assuming I want full synthetic. Car will get 25,000 miles per year. The T-IV is old and not even synthetic, although I've seen that it's a synthetic blend (same as Mobil JWS3309). Any Dexron is a no-no. I don't want MaxLife with its more aggressive seal conditioners because as of now there are no leaks. Castrol Transmax is fully synthetic and supposedly works fine. A bit pricey locally, but I don't want to get it if it's not best for the vehicle.
Then, there's what I WANT to use. It doesn't seem to be too popular, but it's cheap, available and what I use for the older Camry: Valvoline Import Multi-Vehicle Automatic Transmission. It's says Toyota "Type IV" right on the front and I can get it locally $6/quart or $25/gallon. Fully synthetic and has kept the Camry going good from 200k to 350k. It says it's good for Dexron and many other applications though. Would this be the "best"?
The process:
Car is a 2008 FWD and has nearly 300,000 miles and I'm assuming the fluid has been changed before based on its color, but I can't be sure because we've only had it a year. I'm going to drain the pan and put that same amount of fluid back in. I'm going to go with the cheapest for this, which I think it's the Toyota "T-IV" which is $6 at the dealership. Then I'll drive it for a month, then move on to step 2. I'm going to buy a MityVac or Pela oil extractor for $100. I'll try to suck 100% of the fluid out through the dipstick tube. Then I'll drop the pan, clean the magnets, spray brake cleaner on the screen thing, put a new seal on, torque to spec, then refill with the proper amount of fluid.