ATF 3353 vs. Dex III vs. Dex VI

[JHZR2]

Hi,

MB 236.12 ATF is also known as ATF 3353. 236.12 is backwards compatible with the older sheet 236 fluids for MB ATs, and would be applicable for the 722.3 unit in my MB 300CD.

Ive been running Dex III, nothing wrong with that, but why not run a different/better fluid, particularly since Dex III is obsolete and not certified. Especially if the more consistent performance/viscosity of something like Dex VI can be an improvement (and the reduced viscosity might benefit economy too).

Since 3353 is the official MB fluid, and is claimed to be a Dex III type fluid, whatever that means... but is a 6.8 cSt fluid, would dex VI be a good fit?

http://www.opieoils.co.uk/pdfs/New-Fuchs/TITAN-ATF-3353.pdf

Im not tied to MB 236.13/3353 besides the fact that it is the official fluid from MB. However, the original spec was actually dex II. Because of the age and fact that it isnt a GM AT, Im not sure if dex VI will truly, absolutely be compatible. But it seems like 3353 isnt much special, just a lower viscosity, maybe synthetic version of dex III... So might dex VI be the right track?

Maybe the MB TSB can be seen below, but it interestingly shows an older maxlife as an acceptible 236.12 replacement. No official certification that Ive seen... but it seems that the maxlife has been changed to be MB and Dex VI "acceptible".

So is Dex VI my best bet overall?

Thanks!

 

[JHZR2]

Wow, silence. Im inclined to try dex VI in these old, mechanical/vacuum ATs...

So what is the most viscous Dex VI out there?

 

[cmf]

I doubt there's much difference between Dexron III and VI in terms of it's functionality in your transmission. If anything, like you said, the Dexron VI is going to be more modern and higher quality than Dexron III (Dexron III is conventional and VI is full synthetic).

Maxlife seems to work in every transmission, so it might be a good bet for a decent fluid. It says it is "suitable for" Dexron II, III and VI as you noted. Valvoline Dexron VI also says it meets Dexron II and III. I'm sure other manufacturer's offer similar items.

I would not go solely for the "thickest Dexron VI" as they all have to maintain a certain viscosity and the thicker it is originally the more it shears (generally). The only real issue I could imagine is if Dexron VI uses a lot more FM than Dexron II. This would really be something that you would only be able to tell by trying it out.

With all that being said, if it was my car I would use Red Line Synthetic ATF. Other than that I think your best bet is MB forums.

 

[SteveSRT8]

All Dex VI is SEMI synthetic blend except a couple. We use the Valvoline which is full syn formula.

All are the same viscosity, etc., and the new spec is a huge improvement for any trans using Dex III. There are rare cases of issues, but I'll bet the fluid is not at fault. Since Dex III is well known to shear quickly it is for certain that in long/hard/severe service Dex VI will almost always be a superior fluid.

Works great in our fleet of 4L85E's/4L65E's/4L80E's.

 

[JHZR2]

But a 30yo mb 722.3 at isn't a 4l60e. My thought is that it was never desireable for dex 3 to shear down to 6cst. Dex 6 is somewhere mid 6's, but iirc the main parameter of interest was shear stability.

So my basic thought process was that if older ATs were designed for some median viscosity, not dex 3's starting 9ish cst and not dex 6's 6ish cst, I might get the best of all worlds. Thus my hope was kind of for a 7cst dex6 fluid...

Thinking out loud...

 

[SteveSRT8]

Nice idea, but that may require some custom blending!!!

Any 30 year old trans may have lower fluid pressure already and be near a slippage issue therefore making any new fluid a risk taking proposition.

 

[cmf]

Originally Posted By: SteveSRT8
All Dex VI is SEMI synthetic blend except a couple. We use the Valvoline which is full syn formula.


Yeah I see that Castrol lists theirs as synthetic blend. Sorry for the misinformation I was just going off Valvoline. I've never owned or serviced a GM car so my knowledge on them is lacking. Also the nomenclature for synthetic versus synthetic blend versus conventional is awful, but that's an old debate that should stay at rest. I generally give everything the benefit of the doubt because people get upset otherwise.

ATF's shear down relatively fast. It's not that Dexron III was aimed at some median viscosity but rather it was aimed at being ~6 cSt for most of it's service life and started out higher because they used cheap base stocks and the VII's they had back then were easily sheared.

RL Synthetic (they really need to rename it) is 7.2 cSt and synthetic. I understand if you don't want to spend a lot on transmission fluid for a car you barely drive, but I really can't think of anything better.

 

[JHZR2]

I spare no expense really for stuff that will make fragile parts like ATs last >>200k without rebuild. I'm not convinced that RL is the best based upon my experience with their MT fluids.

My transmissions shift like new, and im not worried about a fluid change messing them up. Just want to select the optimal fluid.

 

[Whitewolf]

Originally Posted By: JHZR2
Wow, silence. Im inclined to try dex VI in these old, mechanical/vacuum ATs...

So what is the most viscous Dex VI out there?


Don't confuse viscosity with film thickness.

The average DEXRON-III fluid would start out with a KV 100C of about 7.6cSt but by around 80K miles it would be about 4.1cSt.

DEXRON-VI starts lower (about 6cSt) but does not go much lower than 5.5cSt. That is one of it's design requirments.

 

[JHZR2]

Originally Posted By: Whitewolf


Don't confuse viscosity with film thickness.

The average DEXRON-III fluid would start out with a KV 100C of about 7.6cSt but by around 80K miles it would be about 4.1cSt.

DEXRON-VI starts lower (about 6cSt) but does not go much lower than 5.5cSt. That is one of it's design requirments.


So what do the viscosities you posted stating wrt film thickness?

If I'm replacing fluid every 30k does it really matter?

 

[Whitewolf]

I am just saying that bulk oil viscisity and film thickness do not relate well.

 

[71Chevyguy]

I have been thinking about this myself with the Dex VI being thinnner for use in older transmissions. I hate to say this but I considered using a little bit of Lucas transmission stuff to thicken it up a bit. Not that I believe any of the miracles that Lucas promises but I think we will all agree that it does a very good job thickening.

 

[gomes512]

^ Don't know how much you would have to add to get to the starting cst of Dex3... You'd be diluting the Dex6 with a grpI base. How shear stable is Lucas?

I'd think that instead of adding Lucas you'd be better off with valvoline's maxlife.

 

[NateDN10]

Originally Posted By: gomes512
^ Don't know how much you would have to add to get to the starting cst of Dex3... You'd be diluting the Dex6 with a grpI base. How shear stable is Lucas?

I'd think that instead of adding Lucas you'd be better off with valvoline's maxlife.

According to the PDS, MaxLife is 6.11 cSt at 100C. That's about the same as Dexron VI.

 

[gomes512]

Originally Posted By: NateDN10
Originally Posted By: gomes512
^ Don't know how much you would have to add to get to the starting cst of Dex3... You'd be diluting the Dex6 with a grpI base. How shear stable is Lucas?

I'd think that instead of adding Lucas you'd be better off with valvoline's maxlife.

According to the PDS, MaxLife is 6.11 cSt at 100C. That's about the same as Dexron VI.


Ah, good to know thanks for the heads up.

 

[disturban]

If you have a GM transmission change it out to Dexron VI, I changed the fluid in every car in our family over to Valvoline Dex VI and everyone had over 100k on them, amazing difference in how they all shift now and we have had zero issues...GM's love Dex VI!