DEXRON®-HP spec (GMW16974) published

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Originally Posted By: BigLee
Whitewolf,
Thanks for the info.
I searched, but found nothing on it.
It appears to have no significant difference
in the 40-100C range of viscosity at least,
from Dex6.


No, it's essentially the same in that range. It was invented primarily for fuel economy, whilst retaining durability. On the European test cycle the fuel economy improvement vs normal DEXRON-VI was shown to be over 1%.
 
Originally Posted By: 147_Grain
Could the Dextron-HP have a better more shear stable synthetic base stock than Dex-6?


It is polyalphaolefin. You can pretty much see what it is if you get hold of a copy of the patent 8,642,519B2.
 
So the Dextron-HP is PAO (Polyalphaolefin) based and likely a full synthetic, versus Dex-VI which is a synthetic blend at a minimum.
 
Originally Posted By: 147_Grain
So the Dextron-HP is PAO (Polyalphaolefin) based and likely a full synthetic, versus Dex-VI which is a synthetic blend at a minimum.


PAO is synthetic. Most, if not all, 'normal' DEXRON-VI fluids are mineral. Bear in mind that in North America group III mineral stocks can be and often are legally called synthetic.
 
Yikes, a 5.95 cst @100*C, WAY TOO THIN for the T56!
eek.gif
 
Originally Posted By: 901Memphis
Originally Posted By: dailydriver
Yikes, a 5.95 cst @100*C, WAY TOO THIN for the T56!
eek.gif



The T56 should be using a dedicated MTL


It WOULD have an MTL in it IF Red Line, Amsoil, Motul, etc. would ever make one with < an 8.5 cSt @ 100*C.

I've tried almost all of the others on MolaKule's list, and NONE of them worked well in winter ambients (even when somewhat warm), or until FULLY hot even in summer ambients, so it got the old T56 standby, D4 ATF (one of the most 'stout' Dex 3s in existence).

That being said, this summer, I may give the Amsoil MTF (9.6 cSt @ 100*C) another chance.
wink.gif
 
You could always mix the proper ratio of Amsoil signature ATF with the Amsoil fuel efficient ATF to hit your targeted viscosity range, I'm sure the additive packages are the same and you could ask Amsoil to confirm. Probably just as lighter base oil difference.
 
Originally Posted By: dailydriver
Originally Posted By: 901Memphis
Originally Posted By: dailydriver
Yikes, a 5.95 cst @100*C, WAY TOO THIN for the T56!
eek.gif



The T56 should be using a dedicated MTL


It WOULD have an MTL in it IF Red Line, Amsoil, Motul, etc. would ever make one with < an 8.5 cSt @ 100*C.

I've tried almost all of the others on MolaKule's list, and NONE of them worked well in winter ambients (even when somewhat warm), or until FULLY hot even in summer ambients, so it got the old T56 standby, D4 ATF (one of the most 'stout' Dex 3s in existence).

That being said, this summer, I may give the Amsoil MTF (9.6 cSt @ 100*C) another chance.
wink.gif



You could cut the Amsoil MTF with their ATL in varying ratios to get the desired result.
Back in the old days we tried all sorts of things to get proper synchro operation.
That included mixing SAE 30 motor oil with different types of ATF which were available at the time.
Also Castrol VMX 80w worked extremely well as a dedicated GL 4 gear lube. But it's a mineral oil if your prejudiced.

Alternately if you can get it, something like Penrite Pro Gear 70w-75 is a dedicated synthetic gear oil developed for the T56 type applications.
By all accounts it works very well, as well it should because the relevant viscosities are very similar to DEX II/III.
 
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Originally Posted By: Greasymechtech
At $25/qt, I don't expect it to be in stock in too many autopart stores or wallyworld.



Originally Posted By: Whitewolf
Originally Posted By: BigLee
Whitewolf,
Thanks for the info.
I searched, but found nothing on it.
It appears to have no significant difference
in the 40-100C range of viscosity at least,
from Dex6.


No, it's essentially the same in that range. It was invented primarily for fuel economy, whilst retaining durability. On the European test cycle the fuel economy improvement vs normal DEXRON-VI was shown to be over 1%.



So, for $25/qrt, we can get a 1% fuel economy improvement.
Or, for about 1/5th that price (less than $5/qrt) we can get Dex VI at Walmart.
I susepct any PAO that costs 5x more money is going to have to give me a better pay-back than that.


Here's a hypothetical situation:
2008 Dmax/Alli truck gets an average of 15mpg with DexVI in the tranny.
That same truck then gets 15.15mpg with DexHP in the tranny.
If you drove 10k miles a year, the following would be true -
DexVI would consume 667 gallons of fuel.
DexHP would consume 660 gallons of fuel.
The dF (delta fuel difference) is 7 gallons. At the current price of $3/gallon, that's $21 the DexHP saves in fuel.

The cost of putting fresh DEX VI in the tranny is 7 qrts x $5/qrt = $35. Done twice for a "full" exchange it would be $70.
The cost of using DEX HP in the tranny is 7 qrts x $25/qrt = $175. Done twice for a "full" exchange it would be $350.
In terms of fuel economy, I'm not spending $350 to save $21.


Or we can look at this from the OCI standpoint:
I would expect that DexHP probably has a longer lifecycle; we have no idea what it is at this point. But I do know that DEX VI has a very long lifespan; way past what most folks think it is. Therefore, I don't know if we have an ability to really say how much longer the HP would last over VI in terms of duration of use. In theory, it would have to last 5x longer because it costs 5x more. In terms of fluid OCIs, I don't think one could ever get there. Even if Dex VI lasted 50k miles, the HP would have to last 250k miles to "break even".

From a corporate CAFE point of view it may make sense to do this; they pass the fluid cost to the customer anyway at the time of vehicle sale. But from my garage, from a maintenance perspective, it's a losing proposition. For the OEM, this can make for a good decision. The CAFE improves and the cost is passed on.

In other potential applications, such as small cars, it's still probably not going to greatly alter the ROI enough to warrant a change over to HP.

There are only a few ways a syn can pay for itself:
1) fuel economy
2) fluid longevity
3) wear rate reduction
In some manner, it must do one or more of those in combination to make the ROI work out.

I'm not seeing it here ... I don't see the validation of the need for HP in most circumstances. If it's OEM FF, then it would have to be a lifetime fluid, because replacing it would be silly expensive for essentially no ROI.


In a new car with HP as the FF, I'd leave it in there as long as possible. I'd do a UOA before I dump it because it's far cheaper to UOA than to OCI with HP.

In a used vehicle already using VI, I cannot see the logic in changing over; it won't reduce fuel consumption or wear enough to warrant it's use. It would have to be a "lifetime" replacement fluid, and you'd still struggle to drive enough miles to make it payback the investment.
 
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From an OEM perspective the value of a 1% gain in fuel economy by simply changing the oil is huge when compared to the cost of trying to achieve the same improvement by the engineering route.
 
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I'd say the same for an eco-enivro-weenie. I will probably pick up a quart for my PSF. I was never really impressed with DexronVI and am glad 6HP is available. I'd wager that cost will come down in time. I don't see the point in flushing my Amsoil ATL, Torco, Neo, RoyalPurple, or Redline D6 with the Dex6HP.

I am glad that automakers are catching up to what the boutique manufacturers knew decades ago. Group 4 and 5 base oils are the best! I have to give Amsoil/Redline... the credit that they deserve.

The real question... is there an engineering defect in those 8speed units that require 6HP? will they self destruct on groupIII dexVI? Time will tell.
 
Originally Posted By: Whitewolf
From an OEM perspective the value of a 1% gain in fuel economy by simply changing the oil is huge when compared to the cost of trying to achieve the same improvement by the engineering route.



I completely agree; the OEM can benefit in terms of CAFE. And they will pass the fluid cost onto the customer. It's a "win/win" for them.

But for the guy servicing a DEX VI application in his garage, it is probably not a wise decision. It would obviously be situation-dependent, but given the HUGE cost disparity currently represented, I don't see it being anywhere near capable of providing a good ROI.

I've got about 135 UOAs for the Allison 1000 series tranny. Dex VI does a great job and will last a LONG time. The DexHP would have to exhibit an infinite life-cycle in a very-high-mileage application, just to break even. I suspect other DEX VI app's like the 6L80/6L90 are similar.
 
Originally Posted By: dnewton3
Originally Posted By: Whitewolf
From an OEM perspective the value of a 1% gain in fuel economy by simply changing the oil is huge when compared to the cost of trying to achieve the same improvement by the engineering route.



I completely agree; the OEM can benefit in terms of CAFE. And they will pass the fluid cost onto the customer. It's a "win/win" for them.

But for the guy servicing a DEX VI application in his garage, it is probably not a wise decision. It would obviously be situation-dependent, but given the HUGE cost disparity currently represented, I don't see it being anywhere near capable of providing a good ROI.

I've got about 135 UOAs for the Allison 1000 series tranny. Dex VI does a great job and will last a LONG time. The DexHP would have to exhibit an infinite life-cycle in a very-high-mileage application, just to break even. I suspect other DEX VI app's like the 6L80/6L90 are similar.


For CAFE/Fleet requirements, as Whitewolf stated, that would be true.

But for the average Joe, the current price of the fluid at 4X cost for DexVI would not be conducive to a sensical ROI.
 
Originally Posted By: Ducman
Originally Posted By: dailydriver
Originally Posted By: 901Memphis
Originally Posted By: dailydriver
Yikes, a 5.95 cst @100*C, WAY TOO THIN for the T56!
eek.gif



The T56 should be using a dedicated MTL


It WOULD have an MTL in it IF Red Line, Amsoil, Motul, etc. would ever make one with < an 8.5 cSt @ 100*C.

I've tried almost all of the others on MolaKule's list, and NONE of them worked well in winter ambients (even when somewhat warm), or until FULLY hot even in summer ambients, so it got the old T56 standby, D4 ATF (one of the most 'stout' Dex 3s in existence).

That being said, this summer, I may give the Amsoil MTF (9.6 cSt @ 100*C) another chance.
wink.gif



You could cut the Amsoil MTF with their ATL in varying ratios to get the desired result.
Back in the old days we tried all sorts of things to get proper synchro operation.
That included mixing SAE 30 motor oil with different types of ATF which were available at the time.
Also Castrol VMX 80w worked extremely well as a dedicated GL 4 gear lube. But it's a mineral oil if your prejudiced.

Alternately if you can get it, something like Penrite Pro Gear 70w-75 is a dedicated synthetic gear oil developed for the T56 type applications.
By all accounts it works very well, as well it should because the relevant viscosities are very similar to DEX II/III.


Thanks
thumbsup2.gif
, I will have to call Summit Racing (the ONLY place in the states that even knows what Penrite is) and see IF they can get that, but I fear the co$t (I would expect >$30.00 USD/liter).

I have mixed the Red Line MTL & D4 in the past, but ANY MTL at all will raise the cSt above the requisite Dex 3 level of ~7.5 cSt @ 100*C.

I may try the Amsoil MTF, blended with their Signature Series ATF to at least get thinner yet, since the MTF starts thinner than Red Line's MTL.
 
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