> Synthetic ATF will stand up to much higher temperatures without oxidizing.

That is true. Too bad our application does not subject the ATF to "much higher
temperatures", otherwise the use of synthetic ATF might be of some benefit in
our cars...

Better to make sure the cooling system is functioning properly than to fortify
the car against high temperatures it should never see (unless you make a habit
out of towing trailers out of Death Valley in the Summer in 1st gear, that is).

> It will flow more freely at low temperatures, and it will reduce internal wear.

I've never heard of anyone's AT not flowing (the AT not working) because of
low temperatures. 30 years ago, at -15 dF, it was common for a Dexron-filled
AT's first 2 or 3 shifts to be a little sluggish. But that was a rare situation
for most users, and of no overall significance to transmission (or ATF)
longevity. I'm not sure what is the coldest temp my car's ever woken up to, but
it's never exhibited that sluggish-first-few-shifts behavior (though valve
actuation via solenoids [in modern ATs] rather than fluid pressure probably makes
this a more complete non-issue anyway).

As for reducing internal wear, synthetic engine oil accomplishes that via reduced
friction. But, as I've already pointed out in this thread, ATF must not be too
slippery. So please, Dick, explain to me the "reduce internal wear" dynamics.

> Ideally, you want to replace transmission fluid before it ever shows signs of oxidation (turning brown/smelling badly).

By that logic, Dexron should be replaced every day, because it will show signs
of oxidation after its first use. By that logic, ATs without synethetic ATF
would all be dropping like flies -- you'd encounter one blocking a lane or two
on every rush-hour drive. But since we don't, your logic appears to pertain, at
best, to a theoretical ideal in a perfect world, where everything lasts forever,
but not to the real world.

> With non-synthetic, changing what drops out of the pan every 15-20,000 miles is cheap insurance.

Well, 30 years ago that was true, but due to the advances in Dexron and ATs
(especially lock-up torque converters), it is now totally unnecessary; overkill;
the mark of an obsessive over-maintainer. WORSE, the ATF remaining in the
opened system will have been given a lot of fresh oxygen with which to combine,
which exactly what you do NOT want to do if you are concerned about the longevity
of Dexron. (Dexron ages primarily by comgining with oxygen, which tends to
happen in direct proportion to the presence of elevated temperatures and the
availability of oxygen.)

So I equate your "cheap insurance" with "bad advice".

> If you go back through the old messages, you will find some data provided by one of a Volvo shop mechanic, who routinely tests discolored fluid and in every case the lab said to change the fluid.

That "lab" had a trained monkey who did the tests visually...!

Sounds like yet another obsessively-worrying-about-Dexron waste of money to me,
as it conflicts with not only my experience, but the advice of the auto-maker
(Volvo, who'd have already gone bankrupt if these ATs couldn't go 50+K mi w/o an
ATF change), the AT-maker (Aisin-Warner, whose transmissions have been coveted
by numerous auto manufacturers), and the ATF-maker (GM, maker of Dexron, who says
that modern Dexron can [out-] last the life of the vehicle).

Volvo's leave-it-alone recommendation was not made in a vacuum, but supported and
recommended by the folks who make the ATs and the ATF.

> Best I can recall, he also said that they had not replaced a transmission with good fluid--only those which had bad fluid.

There you go again, confusing cause and effect:

When/as a transmission dies/fails, it kills (overheats; cooks) its ATF through
excess slippage due to transmission malfunction. So if the transmission
malfunctions and needs replacement, it's very likely already killed its ATF. The
fact that they had not replaced a transmission with good fluid does not mean that
constant fluid changes will prevent transmission malfunction. It merely means
that if the transmission does not malfunction, there will not be anything wrong
with the AT or with the ATF.

> Almost everyone on the Saab BB "knows" that the older Saab automatics would need replacement/rebuild after 80-85,000 miles

Almost everyone knows that this does not pertain to our Aisin-Warner
transmissions.

Bottom line: transmissions can kill themselves (and their ATF), but ATF does
not kill transmissions without some kind of abuse or other anomaly.

Dexron dies when/after it is exposed to excessive temperatures. Under anything
approaching normal use, the ATF in our transmissions is not exposed to excessive
temperatures. (If your doctor offered you synthetic blood that would allow you
to remain comfortable in ambient temps of 150 dF, would you be interested?)

I'm happy for you and your Saab transmission, but there is no proof that your
synthetic ATF is in any way responsible for its having lived this long, though,
having purchased a car with a known transmission frailty (actually, it was when
a driver engaged Drive while rolling backwards or Reverse when still rolling
forward, as when rocking the car when it was stuck, that was the known killer
of those transmissions), I'm sure it's given you a little more peace of mind.

But our AW transmissions have no such known frailties. Our AW transmissions are
strong, sturdy, robust...

So, again, a confusion between cause and effect, plus a little misapplied
generalizing across different brands of ATs, plus an unproven believe that a
certain kind of snake oil can be credited for logevity (I cannot prove that the
DurAlt fuel conditioner I use has resulted in an engine that consumes no oil
after 131K mi) can make synthetic ATF seem like some kind of panacea.

Plenty of folks who've experienced failing transmissions have changed their ATF,
hoping to reverse the well-esstablished cause-effect relationship between failing
ATs and burned up ATF. It's never done any good, though it may make the
transmission shifts feel slightly better for a very brief period. I've never
heard of any case in which the AT had problems and had blackened the ATF but how
replacing the standard/black ATF with synethetic cured anything. That's because
thick/black ATF is a symptom (effect), not a cause, of AT problems.

I've run my car hard up Pikes Peak more times than the rest of you combined.
(Running hard, uphill, on the boost, in thin air [lessened cooling] for 20 miles
of switchbacks is as close to towing a trailer out of Death Valley as my car will
ever get.) I have changed the ATF (flushed w/fresh cheap Dexron) exactly once
in 131K mi. I have never sucked/introduced fresh air into my AT's 'closed'
hydraulic system. My car's A-W automatic transmission is doing just fine, thank
you very much.

If you regularly tow a 3000# trailer with your car's Aisin Warner AT, synthetic
ATF would make some sense (though so would a higher capacity transmission
cooler, or a more suitable tow vehicle).

- Dave; '95 854T, 131K mi


PS: I am not a (re)seller of any kind of ATF, nor am in interested in spending
excessive funds in an vain attempt (factually-based or not) to make my car's AT
last 2 million miles.