Which Dexron III fluid should I use?

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Apr 22, 2007
San Jose
I picked up Castrol Dexron III, is this good? I mainly want better shift feel and protection. I've got 88,000 miles if it matters.

and no, I can't use Dexron IV/V/VI/etc. only Dexron III because that's what GM/Tremec calls for, its a T56 6-speed manual and people have reported problems with going with synthetic and newer Dexron fluids
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GM does not recommend using Dexron-VI in the manual transmissions because the manuals were not revalidated with Dexron-VI. This is not to say that Dexron-VI will not work, but rather, GM has not done the testing to recommend it.

With that said, I think Castrol Dexron/Mercon fluid would be fine. There may be better choices, but I'm not familiar with this particular application. Just remember that since Dexron III licenses have expired, so fluids that are advertised to be Dexron III may or may not be the same as before.

PS-- Sam's Club > Costco
AC Delco has a Dex III which is perhaps very very cheap. As long as the can has the word Dex III, any product is OK and go by the lowest price.
Originally Posted By: The Critic
PS-- Sam's Club > Costco


I would personally use Chevron MD-3, but that's because I can get it at Costco for something like $27.50 per case.
Most synthetics are universal or multivehicle ATFs. Simply avoiding those would eliminate all the rumors stereotyping 'synthetic is bad' mental

I wonder how well transynd will do? or any TES389 fluid?

Castrol Dex3 will do you well. It or any other D3 clone should be equivalent.

Redline also has a DexIIe/Merc fluid and racing ATF. Royalpurple has the synchromax. Torco has an MTF.

And, then there are the synchromesh fluids like Amsoil MTF or Redline MTL.
Advance autopart ATF dex-mercon work fine on 500whp friends camaro, and it work fine on 300whp my camaro.
Fluids that meet Allison's TES-389 spec ARE Dexron-III under a different name. Ditto for GM's renamed manual transmission fluid which will be referenced as the replacement the the Dexron-III named fluid.

Or, try one of the manual transmission fluids from Amsoil or Redline.
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