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Which ATF to use now?

 
Old 06-11-2011, 11:36 PM
  #1  
WallyP

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Default Which ATF to use now?

Porsche says that the fluid to be used in the 928 automatic transmissions and power steering systems should be Dexron II(D). Dexron is not a brand, but instead a GM fluid specification and license. If you certified that your fluid met the Dexron II(D) spec and paid GM $3000 per year, you could label your fluid as Dexron II(D). The II(D) spec became obsolete, and was replaced by Dexron III, which went thru a series of minor spec changes, ending with III(H). Dexron III was specified to be backwards-compatible with II(D), but Porsche never changed their specification (or at least not by the 1993 date in my Workshop Manual).

Dexron III(H) is now obsolete, and all GM licenses for the product have expired. There are no fluids on the market that are certified/licensed as Dexron II or III. There are fluids that are recommended for use where the Dexron II or III fluids are specified, but they are not certified or licensed as Dexron.

GM has now introduced Dexron VI, which they say is a much-improved fluid, and is backwards-compatible with Dexron II and Dexron III. The specs are much tougher to meet, and any fluid licensed as Dexron VI should fully meet all of GM's new specs. No pure dino base oil will meet the new specs, so all Dexron VI is at least a synthetic blend.

Here is part of an earlier GM paper on the new fluid.

"GM, Afton and Petro-Canada sought to develop a fluid with a more consistent viscosity profile compared to Dexron-III(H); that would perform more consistently in extreme conditions; and that would degrade less over time. They achieved these improvements, officials said, by raising requirements for oxidative and shear stability, foam performance and protection against pitting.

GM claims that Dexron-VI delivers more than twice the durability and stability in friction tests than do existing fluids. Although the company is still gathering data, it expects this to lead to a drain interval extension of roughly the same order.

“The result [of the effort] is a new fluid that significantly outperforms existing fluids in every aspect,” said Roy Fewkes, driveline fluids group leader for GM Powertrain. “In fact, we have had to significantly extend the length of our durability tests to fully test the fluid’s capability.”

“In every parameter, this is a significant improvement over fluids that are already on the market,” John Sunne, Afton’s director of original equipment manufacturer liaison in Southfield, Mich., told Lube Report. “Meeting all of the requirements was extremely difficult.”

GM said it incorporated fleet tests and the requirement for compatibility with other chemistries to further ensure product performance. But it also acknowledged the difficulty of these requirements.

“We need to make sure there is a consistent product [in the aftermarket], so we’ve set up these additional hurdles,” Kemp said. “[Gaining approvals] is not going to be a simple stroll through the park as has been the case with previous specifications.”

Observers agreed that Dexron-VI is tougher than existing ATF specifications, though some described it as an incremental step in ongoing market trends.

“It will require higher quality base stocks, and the fluid itself will have to be more shear stable,” said Craig Paterson, product manager with Lubrizol Corp.’s ATF segment in Wickliffe, Ohio. “We believe it will take a little bit longer to gain approval, due to the additional tests. There will be a definite increase in costs.”

Changes also have been made to the licensing program. Rather than licensing fluids directly, GM will license chemistries that meet the specification's requirements, leaving it to additive companies to issue sub-licenses for approved finished fluids. Afton, currently the only company with an approved chemistry, said it will not charge separate licensing fees. GM charges an annual fee of $3,000 per product under the old program.

Involvement in the spec appears to be a coup for Petro-Canada and Afton, which won contracts to be exclusive suppliers of base oil and additive chemistry, respectively, for fluid installed in new vehicles. (For factory fill, the fluid is referred to as RDL-3434.) GM began installing the new fluid at its Willow Run plant in Ypsilanti, Mich., April 4 and will convert other facilities in coming months. It also said Dexron-VI will be available through its authorized dealerships and service centers this summer.

The big question is how prevalent Dexron-VI will become in the service fill market, which trumps factory fill volumes. The fluid will become GM’s recommendation for service fill on all cars and light trucks, although not in time for owners manuals of some model year 2006 vehicles. Moreover, the automaker is already recommending Dexron-VI for service fill in existing vehicles, noting its compatibility with transmissions built before model year 2006. To encourage the switch, the company will cease to issue Dexron-III(H) licenses at the end of 2005, meaning all such licenses will expire by the end of 2006."

Now to the interesting parts...
As far as I can find, neither Porsche nor Mercedes has approved Dexron VI for their transmissions. There are many owner reports that the fluid works better than the older Dexron fluids, with better shifting, better cold-weather performance, etc.

GM initially specifically said that Dexron VI was not approved for use in power steering systems or manual transmissions. (There are quite a few manual transmissions that specify Dexron as the lubricant.) I have not yet found whether or not GM ever got around to approving the fluid for these applications.

Allison (a GM company) says that Dexron VI should not be used in their transmissions built before 2006.

Now what?
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Old 06-12-2011, 12:22 AM
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Rick Carter
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Wally, I expect answers from you not questions.
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Old 06-12-2011, 01:59 AM
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borland
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For power steering, I don't think there would be any advantage to using Dexron VI instead of Dexron III.

For the Automatic transmission, the advantage of synthetic blend (Dexron VI) would be longer service life. Assuming you have no leaks, you might never need to replace it.

Its difficult to flushing out all the old fluid. A typical drain and fill on the 4-speed auto can only replace 8 quarts (7.3 liters) of total 10 quarts (9.3 liters), or 80%.

Cost of Dexron VI is considerably more than Dexron III (Quarts price here $7.29USD vs $4.49USD)
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Old 06-12-2011, 04:26 AM
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Another good reason to convert to a stick.
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Old 06-12-2011, 04:36 AM
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What's wrong with continuing to use Mobil 1 Synthetic ATF or other ATFs that were designed for Dexron II applications? My tranny seems to have done well with it.
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Old 06-12-2011, 10:15 AM
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Valvoline High mileage ATF
Walmart has this brand in the big red jugs

I use it my car
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Old 06-12-2011, 10:25 AM
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Originally Posted by Bill Ball View Post
What's wrong with continuing to use Mobil 1 Synthetic ATF or other ATFs that were designed for Dexron II applications? My tranny seems to have done well with it.
Thats what I was wondering or we go stock up....way up

I've had Mobil 1 ATF in my auto box and pwr steering for many years....no worries mate
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Old 06-12-2011, 10:58 AM
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It doesn't sound like the Dex IV will be a problem. Not sure I fully understand the question. Is the assumption that since Porsche has not (yet?) approved it, it therefore must be harmful? Is the lack of an affirmative nod the same as an affirmative indictment? I'm not sure I'd go that far. From everything in the article quoted, it looks like the new stuff is superior to the old stuff, and backwards compatible too.
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Old 06-12-2011, 01:00 PM
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borland
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Originally Posted by Bill Ball View Post
What's wrong with continuing to use Mobil 1 Synthetic ATF or other ATFs that were designed for Dexron II applications? My tranny seems to have done well with it.
Nothing. My 90' S4 owners manual, specifies just "Dexron ATF". Dexron III is the minimum of what's available now as a substitute for "Dexron ATF". If any ATF meets or exceeds the earlier spec, then it will be ok. However some ATF formulations are specifically taylored for certain vehicles, so you can't just substitute any ATF. Friction plates and seals could be affected by using wrong formulations.

Cost of just one quart of Mobil 1 ATF is now $9.50USD, plus shipping at Amazon.com. That's considerably more than the Dexron VI price I listed above.
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Old 06-12-2011, 01:08 PM
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Originally Posted by Want to be View Post
Valvoline High mileage ATF
Walmart has this brand in the big red jugs

I use it my car
That product is just standard ATF with ATF 'stop leak' and 'hardened seal' additives. That's just a short term fix for a transmission that needs rebuilding.
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Old 06-12-2011, 04:50 PM
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Porsche will not issue new approvals for our model right? So I figure anything that meets the approved specs (Dexron IID) is ok. I use Liqui Moly Top Tec 1100 which is compatible with IID and III.
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Old 06-15-2011, 10:59 AM
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I just did a fluid swap on mine right before SITM and I used Mobil 1 Dextron VI. I had some really cheap generic Dex III in there before and with my boosted car and all the WOT tuning last year it overheated and was starting to turn brown. So far everything is good with the Dex VI, smooth shifts normally, firm shifts at WOT and no leaks.
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Old 06-15-2011, 12:18 PM
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Originally Posted by Cosmo Kramer View Post
I just did a fluid swap on mine right before SITM and I used Mobil 1 Dextron VI. I had some really cheap generic Dex III in there before and with my boosted car and all the WOT tuning last year it overheated and was starting to turn brown. So far everything is good with the Dex VI, smooth shifts normally, firm shifts at WOT and no leaks.
Mobil only makes a Dexron VI in synthetic blend. Mobil 1 ATF is fully synthetic. So, which did you use?

http://www.mobiloil.com/USA-English/...on_VI_ATF.aspx
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Old 06-15-2011, 12:27 PM
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Dextron VI synthetic blend.

Originally Posted by borland View Post
Mobil only makes a Dexron VI in synthetic blend. Mobil 1 ATF is fully synthetic. So, which did you use?

http://www.mobiloil.com/USA-English/...on_VI_ATF.aspx
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Old 06-15-2011, 01:04 PM
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I have been using Dexron VI in the transmission and my power steering for going on 3 years now. I have not had any problems, but rather improved smoother shifting.
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