Can Dexron III & VI be mixed?
Can't find decent brand Dexron III in my area.
I'm doing a tranny filter change on my 98 auto, can I just top it off with DexronVI.
I don't want to do a flush cause the tranny has 95k on it.
I've had bad expireince with flushes and I've read here where some members do not recomend it on high mileage car.
I really want to use Amsoil but the flush thing scares me.

 

Anyone?

 

YOUR CORRECT YOU DO NOT WANT TO FLUSH IT.just change the filter.HAD MY 02 CHEVY S-10 FLUSHED FEW YEARS AGO AND WAS NEVER THE SAME SINCE.

 

There are a number of ATFs that are easily/readily available that meet the Dex III spec. including a couple fine synthetic ATFs like Amsoil and Red Line.

Amsoil: Torque Drive (best) of the Amsoil ATFs, and their ATF is excellent as well.

Red Line: High-Temp ATF, D4ATF or D6ATF.

HTH

 

Use CASE tranny fluid, has a rating of 500* instead of 300* for Dextron and the thickness difference is minimal been doing so for the last year. The tranny performs great.

 

GM states that for your auto, use Dexron VI. No one makes Dexron III anymore. GM no longer licenses the name so anyone can use it in any form, like Dex 3 Dex III Dexron III and it means nothing and guarantees nothing. I would highly suggest any well known brand that complies with Dexron VI. You won't be disapointed, Dexron VI is great stuff! Way better than Dexron III ever was.

 

I have been out of it of a few years and lots have change.
I'll use the VI and feel good about it.
I would love to go Amsoil, but I've been told that I can't mix sethentic with dexron and have to accomplish a flush.

 

Dexron is the "formula" or "recipe" so-to-speak, and can be made using either conventional (mineral base stock) oils OR synthetic materials. Common misperception. Btw, "flushing" is not necessary but would however give you the maximum benefits of a synthetic fluid vs mineral fluid.

In order to use the word "Dexron" or market their product as "Dexron", anyone has to pay GM and get a license and be subject to testing by them. Since GM no longer licenses Dex III, a number of manufacturers still manufacture the same product they were before, but can now only say "meets" Dexron III specs, or "recommended for applications requiring Dexron III", etc. (or words to that effect) for legal reasons. They cannot market their product as "this is Dexron III", but it doesn't mean anything changed in their formulation. Same for Dex VI. Dexron name is a GM trademarked name. At this point it really boils down to the reputation of the company (or companies) producing a product that is "recommended for applications requiring Dex III". Both Amsoil and Red Line (among others) have excellent reputations but Amsoil and RL choose to specialize in synthetic products only.

I did notice that one of the Red Line products meets BOTH specs, but (as per above) has to say "Designed to satisfy Dexron VI, Dexron III, Dexron II, etc, etc....." in order to keep GM's lawyers off their backs.

http://www.redlineoil.com/product.aspx?pid=115&pcid=9

Dexron VI was created for one reason, to maximize fuel economy. If it accomplishes that goal and provides all the other necessary functions of a good transmission oil, so much the better.

HTH

Btw, Amsoil ATL satisfies Dex VI and Dex III requirements as well.

 

Let Me Google That For You

Click the link above then click on the first link once the Google results appear. It's a GM doc on approved Dex VI fluids.



I just did a Dex VI service with Castrol. Used a Delco Filter & Gasket kit also. Shifts fine!

 

All DEXRON®-III licenses expire at the end of 2006 and will not be renewed. Beyond that date GM will only support the use of DEXRON®-VI fluids for use in Hydra-Matic transmissions. Fluids sold in the market after that date bearing claims such as “suitable for use in DEXRON®-III applications” or similar wording should be avoided. DEXRON®-VI licensed fluids are fully backward compatible and can be used in all applications covered by earlier GM ATF specifications.

The use of unlicensed fluids and/or non GM approved aftermarket additives may prove detrimental to transmission performance and void warranty coverage.

If you wish to download the complete doc go HERE

 

GM's marketing machine at work. Of COURSE their going to say "should be avoided". What else WOULD they say?

Much of the above info is basically, but not completely, true, but GM would have the motoring public think that ONLY a GM licensed product is "safe" for their car. This is much the same tactic that ultimately led to things like the Magnuson-Moss Act years ago. The untrue part is the part about use "in all GM applications". Oops, forgot about the 100s of thousands of earlier T-56 standard transmissions out there that ALSO specified Dex III originally and NOT "backward compatible".

 

GM can say that Dex VI is backwards compatible, but this is the same company that when Dex VI came out recommended it for both manuals and autos, then found out it didn't work with manuals and re-released Dex III under new part number 88861800. So while Dex III does now longer exist, there is a new part that does meet the same specs that Dex III once did.

I would also note that Dex VI viscosity is about 40% below that of Dex III (when new) and is designed to help GM with CAFE. The philosophy behind this I believe is that Dex III fluids did not require any specific basestock and most sheared down in viscosity about 40% very rapidly thus are near where Dex VI starts. As Dex VI requires probably a semi-synthetic, the shear down rate is likely slower and thus GM's recommendation that it can be backwards compatible.

But, to me, shear down can easily be avoided by using a good Group IV PAO basestock fluid like AMSOIL.

And contrary to what you have been told, you can mix basestocks. I would use a Dex III fluid like the AMSOIL Universal ATF (Product Code ATFQT) for the C5 auto and do a drain and fill (vice flush) which is what I do in my own autos - I have done drain and fill in my 08 GMC 3500 HD, 07 GMC C5500 (RV) and my 03 Chevy Trailblazer, all with AMSOIL synthetic tranny fluids - no problems.

 

I agree. The engineers at GM don't have a clue. Thank God Amsoil has it all figured out.......

 

Texas refinery is what we use and lots of it for the combines and other crap on the farm. they have amazing stuff!!