A541E - Use Toyota Dex III or something else (better)?

[BrendanC]

Would that be a problem with a multi vehicle dex 3s that are non synthetic only, or would synthetic multi vehicle dex3s suffer the same issue?

Mobil 1 atf has two synthetic variants. One that is recommended in older applications and meet dex 3H, while a newer model transmissions that meet dex hp.

For reference Kinematic Viscosity @ 100 C, mm2/s, ASTM D445 (valvoline doesnt publish astm only mobil)
Maxlife starts out at 5.9
import starts out at 6.7
Mobil dex3h starts out at 7.4
Mobile dex hp starts out at 5.7


For completeness sake i lack of understanding of the differences between dex 3 vs dex 3h.

Dex III as a whole shears out of grade very quickly. it is a great fluid and many high performance GM transmission builders require it be used but changed frequently due to the shearing. for daily drivers, dex VI will stay in grade much longer and require less frequent fluid changes. Yank converters requires the use of none synthetic dex III but i chose to run dex VI as i don’t want to drain and refil 4 gallons of trans fluid every other month. when they cut my converter apart for a cut and clean he said the clutches still looked brand new. Dex VI really is an improvement over Dex III unless you’re drag racing everyday.

 

[kschachn]

Would that be a problem with a multi vehicle dex 3s that are non synthetic only, or would synthetic multi vehicle dex3s suffer the same issue?

Mobil 1 atf has two synthetic variants. One that is recommended in older applications and meet dex 3H, while a newer model transmissions that meet dex hp.

For reference Kinematic Viscosity @ 100 C, mm2/s, ASTM D445 (valvoline doesnt publish astm only mobil)
Maxlife starts out at 5.9
import starts out at 6.7
Mobil dex3h starts out at 7.4
Mobile dex hp starts out at 5.7


For completeness sake i lack understanding of the differences between dex 3 vs dex 3h.

That would be entirely dependent on the brand and upon the quality of the VM used by the blender. The license specifies a maximum deviation. Of course that also means the fluid is licensed, which does not apply to any current "DEXRON-III" fluids. At that point you're dependent upon the integrity and reputation of the blender.

The only real fact is that a licensed DEXRON-VI fluid is better in every respect over a prior license category.

 

[barkingspider]

I would use any dex/merc or Mobil 1 atf and drain and fill at 30k ish

 

[BrendanC]

i do a “spill and fill” once a year. ATF is expensive but transmissions are much more expensive in comparison.

 

[ripcord]

It doesn't matter. If Toyota is using that license in their manual as the proper fluid for their transmission then it's irrelevant. It isn't simply that GM may have said DEXRON-VI is the proper replacement for their vehicles, it's also that a DEXRON-III license is no longer available from the holder.

Sure Toyota sells a branded fluid but that isn't what's listed in the manual. Fluid with a DEXRON-III license is listed and per the license organization that has been superseded.

That's kind of irrelevant. Licenses aside, it's not like the oil manufacturers "forgot" how to make Dexron III. We can be absolutely certain that what Valvoline and others sell as DexMerc is functionally the same stuff as before. They just can't label it as Dexron or Mercon. GM and Ford don't have a strangle hold on a formula, just the their respective trademarks.

 

[LexusToyotanut]

My 01 tundra a340 calls for dex 3, I use valvoine dex merc 3 in it, and it loves it. With the old Toyota dex merc spec you and can any dex merc

 

[nthach]

That's kind of irrelevant. Licenses aside, it's not like the oil manufacturers "forgot" how to make Dexron III. We can be absolutely certain that what Valvoline and others sell as DexMerc is functionally the same stuff as before. They just can't label it as Dexron or Mercon. GM and Ford don't have a strangle hold on a formula, just the their respective trademarks.

Lubrizol and Afton still make DIII/Mercon add packs but they “self-certify” for those specs since official licensing isn’t available. Dex VI/Mercon LV and Dex ULV/Mercon ULV as well as Mercon V(probably not for long) are still licensed by Ford and GM - probably the same means as Mopar - a blender has to buy an approved add pack from Afton or Lubrizol and submit to Center for Quality Assurance for a test and a license #.

In OP’s case, I’d use Castrol IMV. I’ve tried MaxLife in older Toyota transmissions and didn’t like the shift feel. IMV isn’t a “synthetic” fluid but it’s a match for T-IV/DIII viscosity wise. Castrol Transmax Universal seems to be a match as well.