I have an 03 Saturn Vue 3.0 V6, which has an Aisin (Toyota) transmission.

The manual says under normal duty the transmission requires no maintenance. They say the customer cannot check the fluid himself, and it never requires changing. But I found the dipstick; its just short, low, and by the exhaust.

The manual says it takes special transmission fluid, and to contact the dealer for it. A few years ago I called the dealer and they said to use Dex/Merc. I was suspicious, but followed their advice. I did a drain/refill with Penzoil YB Dex/Merc at 60k. Then again around 100k (7k ago).

I have figured out it officially is supposed to have Saturn T-IV, which I assume to be the same as Toyota T-IV (JWS 3309) since it is an Aisin transmission.

Googling about, I've found some people terrified of mixing the two. Recommending a flush after mixing.

But now that the spec has been out a while, there are now some multi-spec'd ATFs. (link)
Some that include Dex/Merc as well as T-IV are:
Valvoline Maxlife, PENNZOIL MULTI-VEHICLE ATF, CASTROL IMPORT MULTIVEHICLE, Chevron Multi-Vehicle ATF (this one even includes Toyota WS). Some bottles of Mobil 1 full synthetic claim T-IV as well.

Since there are now multi-spec'd oils that meet both, I don't think there can be a chemical incompatibility. So I'm disregarding the “if you put a cup of dex/merc in it you must flush” statements.

It looks to me like T-IV is a backwards compatible improvement over Dex/Merc. Maybe higher temp ratings, maybe better additives, but something like that. Compatible, but higher rated.

From now on, I'll be sure to get fluids spec'd for T-IV. But I'm not inclined to freak out about the dex/merc thats in it now. I'll probably keep on a fairly short drain refill interval (20k-30k).

So, experts, what do you think? Should I try to get T-IV in it ASAP?

How much is Saturn charging T-IV? If it is Aisin transmission and the Pontiac Vibe (Toyota Matrix) recommend the same type (or same) fluid, then it is most likely the same fluid as JWS 3309 (Toyota T-IV).

Are you noticing any hard shifting?

No, shifting is fine.

Just bought a case of T-IV for 60 bucks with shipping from Ebay. I figure 5 bucks a quart isn't bad.

My Totota dealer charges me $5.18/qt for T-IV. Shop around and you will find it for a similar price.

Around 5 bucks a quart seems to be the going rate pretty much anywhere I have found. You can also find the Mobil 3309 ATF (same as T-IV) for similar prices.

Right, now that I know what I need, I'll be sure and only use T-IV.

But how concerned should I be about whats in it now?

Thanks,
Joe

Should be fine, as long as you are ok with the shift quality. Most universal ATF, the non OEM, protects good enough but not comfortable enough in shift quality.

I think most people that have used Amsoil and Redline ATFs might disagree with you on the shift quality.

MaxATF from RP users would disagree too.

ok, thanks guys!

The T-IV compatible Universal fluids are not 100% identical to the DEX/MERC only fluids, so it'd be wrong to assume that the two are completely interchangeable.

Just because the fluid allows to the transmission to shift "OK" does not mean that it is optimal. Tractor fluid might shift "OK" in my transmission, but does that mean it will deliver good wear in the long run?

I guess the best way to determine whether or not DEX/MERC is doing the job for you is to do a fluid analysis. But in order to arrive at an accurate conclusion, you would've needed to know what the normal wear pattern for an AF33 is with T-IV. You don't have that.

So to play itself, my suggestion is to flush the system ASAP with T-IV. 12 quarts of T-IV shouldn't cost you more than the equivalent of two tanks of gas, and you would not longer need to worry about whether or not you are continuing to damage your transmission with the incorrect fluid.

T-IV isnt even a good ATF. I have seen plenty of less than impressive UOA's using this OEM fluid. There are plenty of people who have used replacements such as Amsoil and red Line with great success. I use a synthetic replacement for T-IV and it reduced not only wear but improved the shift characteristics. Do you own a vehicle with T-IV in it or did you just google your response as usual?!

As usual? Excuse me, but I do not google any of my responses nor do I pull them out of my (fill in the blank).

And what do you mean by less than impressive UOAs? I'm quite certain that most of us on here aren't even qualified to properly interpret an UOA, therefore, how can I take your response seriously? I'm not qualified to properly interpret an UOA, and I won't pretend than I am. I leave it to more qualified individuals who have done the research and I just follow their recommendations.