Where to get real Dexron III ?

[Jimzz]

Dex/Merc is Dex3. GM does not license Dexron 3 anymore so they call it Dex/Merc.

This is a good one I use for some older cars.
https://www.walmart.com/ip/Super-Tech-High-Mileage-Automatic-Transmission-Fluid-1-qt/17133890

 

[71Chevyguy]

I have run into this in the past. I ended up using MerconV for one vehicle since it was supposed to be DexIII, but semi syn, with a better add package to help lockup converters. Never had any issues with that tranny. I now have several old GM cars calling for DexIII and they got Maxlife LV with a quarter of a bottle of Lucas trans fix or whatever they call it. I doubt there is much of anything in the Lucas that would be negative since it isn't a stop leak or anything. That little bit did thicken it up just enough to get shifts back to normal. Both my 98 LeSabre and 85 Skylark had odd inconsistent shifts on just DexVI. Although I will say the torque converters locked up better on just DexVI.

 

[MolaKule]

Originally Posted by 69GTX
...
Viscosity of 5.8 cSt at 100 deg C for Dex 6 vs 7.4 cSt for Dex 3/Mercon/Mercon V. That extra viscosity was put there for a reason.


They had to start at 7.5 cSt to keep the fluid from shearing below 4.2 cSt up to 30k miles.


Quote
Here are some facts and specifications about these Dexron fluids:

Dex III/Mercon type fluids: Max cSt 7.5; shears down to 4.2 cSt under standard tests;

GM Dexron VI: Starting viscosity cannot be > than 6.4 cSt; cannot shear down to less than 5.5 cST under standard tests;

Mobil 1 Dexron VI: Starting viscosity - 5.83 cSt, cannot shear down to less than 5.5 cST under standard tests;

MaxLife ATF: Starting viscosity - 5.91 cSt, cannot shear down to less than 5.5 cST under standard tests;

Redline D6 ATF: Starting viscosity - 6.4 cSt, cannot shear down to less than 6.1 cST under standard tests.

Shear testing is done using four tests; the Fuel Injector Shear Stability test, the Sonic shear test, the DEXRON®-III Cycling test and the KRL test.

The KRL tests have been shown to provide the better accelerated shear tests, in which all of the above fluids have been subjected.


Let's look at some of the Dexron III(H) and Dexron VI stats. Dexron III(H) is 1.4 cSt higher at 100C than Dexron VI but:

Starting Viscosities@100Cexron III(H) 7.3 cSt, Dexron VI - 5.9 cSt

Shear Stability (~ 10k miles): Dexron III(H) - 4.5 cSt, Dexron VI - 5.8 cSt

Shear Stability .(>=35k): Dexron III(H) - 4.3 cSt, Dexron VI - 5.5 cSt

Dexron III(H) has dropped over 2.8 cSt while Dexron VI has remained stable with only a 0.4 cSt drop. Dexron VI is superior in terms of viscosity stability.

Friction Modification Stability: In Dyno tests, Dynamic friction coefficient change: Dexron III(H) -~ 3%, Dexron VI - ~ 0.05%. Dexron VI is superior in terms of Dynamic friction coefficient stability.

Dexron III(H) uses older Anti-Oxidant and Metal Inhibitor chemistry. Dexron VI uses modern Anti-Oxidant and Metal Inhibitor chemistry.

Dexron III(H) uses older Anti-Wear chemistry. Dexron VI uses modern Anti-Wear chemistry.

 

[anndel]

I bought Mobil 1 Synthetic Multi-Vehicle ATF from Amazon since I couldn't find it here locally. I changed the PS fluid on our 1993 Toyota pickup which called for Dextron II ATF. So far so good, no leaks or strange noises when I turn the steering wheel.

 

[caprice_2nv]

I'm almost positive I'm running ac Delco dexron 6 in my 273k mile gm 2004R transmission. I didn't know about viscosity difference and just assumed it was the better fluid. I can't say about the difference in shifts because before the fluid change it was in the parts car I bought and it had mushy shifts because the TV cable was stretched. Once we swapped it into my 83 we had to modify the TV cable to get optimal line pressure. It shifts probably as good as it would have when new.

In my other 2004R I've used mercon 5 for the first several changes and then dexron 6 and I can't remember what I used last time. It might have been Pennzoil multi vehicle synthetic fluid. No issues with either transmission despite both being over 250k miles.

 

[dave1251]

Originally Posted by das_peikko
Dexron III is getting impossible to find. Reading This Thread has informed me that Dexron VI is thinner than Dexron III. The last time I bought transmission fluid was in 2017 when Walmart had Dexron III labelled as "Automatic Transmission Fluid" but now it doesn't exist. I don't feel like gambling with a substitute fluid like Dexron VI at this time. Please tell me where I can get Dexron III.



There is no gamble using DEXRON VI it is a better fluid in everyway compared to DEXRON III.

 

[Dave1027]

Originally Posted by GON
That is the point- there are no longer any DEX III standards. Go with DEX VI and call it a day.


I can tell you my car does not do well with Dex VI. It's thinner viscosity made it not compatible. Had to use a Dex III compatible ATF. I tried many. This Pennzoil High mileage full synthetic ATF is my favorite:
https://www.pennzoil.com/en_us/prod...LzIwMTZuZXdzbGV0dGVyLz9sb2NhbGU9ZW5fdXM=

 

[dave1251]

Originally Posted by 69GTX
Originally Posted by addyguy
Originally Posted by cronk
The dex/merc fluid from walmart, napa, auto value, etc, is going to be the old dex3 fluid.
I just saw it in walmart in both supertech and valvoline brands 2 days ago.
If it is labeled dex/merc it is NOT dex 6.



+1. Dex VI is a separate product.


Viscosity of 5.8 cSt at 100 deg C for Dex 6 vs 7.4 cSt for Dex 3/Mercon/Mercon V. That extra viscosity was put there for a reason.



Yeah because it shears badly.

 

[hatt]

Originally Posted by MolaKule
Originally Posted by 69GTX
...
Viscosity of 5.8 cSt at 100 deg C for Dex 6 vs 7.4 cSt for Dex 3/Mercon/Mercon V. That extra viscosity was put there for a reason.


They had to start at 7.5 cSt to keep the fluid from shearing below 4.2 cSt up to 30k miles.


Quote
Here are some facts and specifications about these Dexron fluids:

Dex III/Mercon type fluids: Max cSt 7.5; shears down to 4.2 cSt under standard tests;

GM Dexron VI: Starting viscosity cannot be > than 6.4 cSt; cannot shear down to less than 5.5 cST under standard tests;

Mobil 1 Dexron VI: Starting viscosity - 5.83 cSt, cannot shear down to less than 5.5 cST under standard tests;

MaxLife ATF: Starting viscosity - 5.91 cSt, cannot shear down to less than 5.5 cST under standard tests;

Redline D6 ATF: Starting viscosity - 6.4 cSt, cannot shear down to less than 6.1 cST under standard tests.

Shear testing is done using four tests; the Fuel Injector Shear Stability test, the Sonic shear test, the DEXRON®-III Cycling test and the KRL test.

The KRL tests have been shown to provide the better accelerated shear tests, in which all of the above fluids have been subjected.


Let's look at some of the Dexron III(H) and Dexron VI stats. Dexron III(H) is 1.4 cSt higher at 100C than Dexron VI but:

Starting Viscosities@100Cexron III(H) 7.3 cSt, Dexron VI - 5.9 cSt

Shear Stability (~ 10k miles): Dexron III(H) - 4.5 cSt, Dexron VI - 5.8 cSt

Shear Stability .(>=35k): Dexron III(H) - 4.3 cSt, Dexron VI - 5.5 cSt

Dexron III(H) has dropped over 2.8 cSt while Dexron VI has remained stable with only a 0.4 cSt drop. Dexron VI is superior in terms of viscosity stability.

Friction Modification Stability: In Dyno tests, Dynamic friction coefficient change: Dexron III(H) -~ 3%, Dexron VI - ~ 0.05%. Dexron VI is superior in terms of Dynamic friction coefficient stability.

Dexron III(H) uses older Anti-Oxidant and Metal Inhibitor chemistry. Dexron VI uses modern Anti-Oxidant and Metal Inhibitor chemistry.

Dexron III(H) uses older Anti-Wear chemistry. Dexron VI uses modern Anti-Wear chemistry.


What brand Dex III are they using?

 

[dave1251]

Originally Posted by Dave1027
Originally Posted by GON
That is the point- there are no longer any DEX III standards. Go with DEX VI and call it a day.


I can tell you my car does not do well with Dex VI. It's thinner viscosity made it not compatible. Had to use a Dex III compatible ATF. I tried many. This Pennzoil High mileage full synthetic ATF is my favorite:
https://www.pennzoil.com/en_us/prod...LzIwMTZuZXdzbGV0dGVyLz9sb2NhbGU9ZW5fdXM=



How because in use DEX III is thinner than DEX VI your mind is totally trumping reality.

 

[vssjim]

MD3 from Chevron/Havoline is not a Dex 6 spec oil

 

[Jetsfan421]

Ac delco makes a atf type 3h. I would assume its OEM dex3. That or its really close. Only place to get it for a reasonable price is rockauto. I have a 4t65e that likes castrol Dex/merc transmax with lubegard red. If using a Dex/merc its almost necessary to use the lg red.

 

[JHZR2]

Originally Posted by mattwithcats
Get some TES-295 fluid...

https://www.allisontransmission.com/parts-service/approved-fluids/on-highway-fluids

Look for Delvac ATF on Summit Racing, good price...

Cheaper alternative is blue jug of Valvoline Maxlife...

https://www.walmart.com/ip/Valvoline-DEX-MERC-Automatic-Transmission-Fluid-1-Gallon/15125788


I agree. A retired Allison fluids engineer has pointed out that, "DEXRON-III ATFs should no longer be used because none of them are licensed products anymore so no one at GM or Allison has reviewed the data. You don't really know what you're getting... It's just not a good idea to run these fluids anymore unless they're on the Allison TES-389 approved fluids list on the Allison website (Allison Transmission)."

I'd argue that this is the best method of ensuring Dex iii legacy performance.

While I'd generally trust the majors to keep their Dex/merc add packages the same, you never know.

Dex VI can also have interactions with viton seals, so that's a consideration too..

 

[Snagglefoot]

Castrol Dex/Merc.

 

[thescreensavers]

Pennzoil 1 qt. Dexron III Mercon Automatic Transmission Fluid
https://www.homedepot.com/p/Pennzoi...omatic-Transmission-Fluid-3312/204786791

 

[HowAboutThis]

Put NAPA brand ATF in a Subaru 25k ago. Says all the Dexrons on it. Pretty sure the VI works for III. If you're really worried, get OEM. But it's probably the same scenario.

Personally, I'm not worried.

 

[Dave1027]

Originally Posted by dave1251
Originally Posted by Dave1027
Originally Posted by GON
That is the point- there are no longer any DEX III standards. Go with DEX VI and call it a day.


I can tell you my car does not do well with Dex VI. It's thinner viscosity made it not compatible. Had to use a Dex III compatible ATF. I tried many. This Pennzoil High mileage full synthetic ATF is my favorite:
https://www.pennzoil.com/en_us/prod...LzIwMTZuZXdzbGV0dGVyLz9sb2NhbGU9ZW5fdXM=



How because in use DEX III is thinner than DEX VI your mind is totally trumping reality.


The reality is the thin Dex VI was making the car not want to move after cold starts. Using Dex III compatible fluid solved that issue. My car's transmission was designed to use Dex III.

 

[dave1251]

Then your car can't run after 10K miles of DEXRON III use if it can't run on DEXRON VI. So you must be the guy doing a drain and fill every 5K.

 

[Dave1027]

Originally Posted by dave1251
Then your car can't run after 10K miles of DEXRON III use if it can't run on DEXRON VI. So you must be the guy doing a drain and fill every 5K.

Nope. Wrong again.

 

[caprice_2nv]

Guess we will see lol. Your transmission must have some real wear if what you're saying is true. My 1986 and 1989 transmissions with very high miles (one ran at the drag strip occasionally for several years) and they both have no issues on dexron 6. They also were "designed for dexron 3" obviously.

My next fluid change might be a dexron 3 for price reasons since it takes 12L for a complete flush and I have left it longer than my usual 30k mile changes. But so far both transmissions are working perfectly with over 30k on dexron 6. So dexron 6 imo is not generally a problem since myself and many others have had no issue using it in old transmissions.