Dexron III fluid, Dexron/Mercon/ Dexron VI

For the cars that were originally Dexron III, is Dexron/Mercon fluid a suitable replacement?

I've seen some say no, and to just go to Dexron VI.

Others indicate the Dexron/Mercon fluids are okay.

And what about the Walmart Tech Dexron VI fluid which is a good amount cheaper? Is it just as good as a name brand of Dexron VI?

I'm ready to drain and refill my own trans in my 2003 at 115K mi for the 3rd or 4th time. Which should I use?

The Walmart brand Dexron VI is actually better than some of the name brands. SuperTech licensed the patent and is producing genuine Dexron VI and not just a "Dexron VI equivalent".

I just did mine this weekend, I only use Dexron VI from the dealer. It's slightly more expensive that way but well worth the investment. The last change was 75k miles, this one at 150k, trans is still going strong even with my spirited driving style :)

When I rebuilt the trans on my 2000 I dumped Walmart fluid in it and the clutches started slipping after 25k miles. It probably had nothing to do with the fluid but psychologically I feel good about using Delco brand Dexron VI from the dealer.

Don't let them talk you out of buying 8 or 9 quarts. I ran a quart short this weekend and I'll have to go back to get more tomorrow when the dealer opens. All told I got 8.5 quarts out of it without touching the torque converter. I just drop the pan and install a new dealer filter and I always end up replacing 8.5 quarts. The guy at the dealer talked me into only buying 6 and I had 1 sitting around from the last time. I guess I'm a sucker for bad advice, haha.

PS if you go to the dealer double check and make sure they don't sell you T-IV fluid, which is totally different from Dexron VI. The guy initially handed me a box of 6 quarts, when I got home and opened it, I had six quarts of Toyota T-IV. GM sells T-IV for the Pontiac Aztech and a couple other models that happen to use Toyota spec fluid. That would be worse than dumping Walmart fluid in it.