was $1300. Just the fluid change. Had the filter changed late last year around 7500 mile mark.

 

beautifully said, it is exactly defining someone like me.

 

I'm looking to do my first DCT fluid change on my 2021 Stingray Non-Z51. Does anyone know if it's okay to mix Motul High Torque DCT FFL-4 fluid with the AC Delco FFL-4 fluid that was filled in the car from factory? I'll likely be doing the drain and fill. Just curious if anyone has used a different kind of DCT fluid and can confirm that they haven't had any issues. Thanks!

 

Hmm, the 1st DCT fluid change was due in 2024 as it's required every 3 years regardless of miles. I've read much of the info re using other then the GM fluid. For a few bucks I would NOT take a chance. Recall @Andybump comment that you can't trust an SDS sheet when comparing fluids. Was remined how I convinced our safety and heath folks in the largest US Industrial gas company a new shielding gas mixture we were launching, for marketing reasons we did not want to divulge the exact composition (as was listed for all other gases products.) My cousin was GM of a large cosmetic manufacturing facility. Asked how they avoid divulging all their proprietary compositions. He said easy! You have to say, for example, your face cream product contains less than 2 mg/kg arsenic (that is the actual FDA level allowed) not that yours has 1 mg/kg etc. Just have to say it contains less than a value under the max allowed. So our SDS read less than 10% X, less than 5% Y in that case balance Argon. The total was more than 100%. Legal and from a user safety or firefighter concern, sufficient for decision making.

Consider some DCT's by say Porsche that uses separate fluids for the clutches and gears. That allows a lower viscosity different composition fluid for the multiplate clutches and higher viscosity gears. Tremec uses ONE fluid for both. It's a relatively low viscosity fluid similar to that used by slushbox automatics. No doubt needed for a key feature for clutches, keeping them cool as they slip on engagement. For gears there are many additives used to compensate for the low viscosity fluid to handle higher loads, like extreme pressure lubricants, shear stability, friction modifiers, antioxidants, anti-wear agents, detergents/dispersants etc. One many page technical source I found stated up to 20% of the fluid can be additives and some expensive.

With a 2021 your close to being past the GM warranty. IF the DCT needs replacement currently that is a $20,000 bill for a new one. Heck, I self insure myself for many things BUT for $20,000, I'd buy the GM specified fluid, cheap insurance for at least while you still have some GM warranty left. If doing yourself see some on the Internet from a trusted source for $33/Liter.

 

I'd contact Motul and ask them if it isn't disclosed in their literature. Valvoline has stated that it is OK to mix their fluid with the residual fluid left after a drain.

 

I have had 4 Vettes and the maintenence schedule on these C8s in crazy. From what I'm told, the DCT fluid only has a three year shelf life and it's $45/quart.

 

Cost:

for me it was $750 for the fluid and the filter. the majority of the $700 was $400 for 'labor'.

 

That’s been the case for 7 model years.

 

Yes the AC Delco FFL-4 fluid has a 3 year shelf life and the car's maintenance schedule has a 3 year drain and fill schedule. They happen to both be 3 years. And while you may find the fluid at $45 a LITER that is a random price as the price is $22.79 at Rock Auto and has been reported to hover around $50/ liter at Chevy dealers.

 

$22/ltr at RockAuto. Filter is about $100. You can do yourself for about $350. So it'll cost you a little over $100/yr to maintain the DCT. Skip a dinner out once a year and you're good to go.

 

$750 for changing the filter and fluid including labor is how I read your post but then you say $700? And if labor was $400 that means you paid $350 for parts, filter and fluid. Considering the filter is a $200 part and fluid $50/ liter (usually 9-10 liters) at dealer full price you got a great, nay, awesome deal.

 

I don't recall saying "you can't trust an SDS (safety data sheets)." I did say one must understand what the term Full Synthetic, found in product advertising and Product Data Sheets (PDS), does not necessarily mean that the product is made from laboratory engineered and manufactured hydrocarbon compounds (Esters and Polyalphaolefins) which would be Group IV and Group V oils, but rather could be made from highly refined crude oil, referred to as Group III oils. And I said that the Safety Data Sheet (SDS) offers clues to the content of a product. Since the 1990's (so it really should be common knowledge by now), Group III oils can be referred to as Full Synthetic because it was determined that they perform as well as the engineered products (not my words, that was just the ruling).

So anyway, the question is about mixing the Motul High Torque DCTF with residual OEM fluid in the transmission when changing the fluid. Here is a product data sheet of sorts for that Motul Product:

https://azupim01.motul.com/media/mot...5_20220505.pdf

This data sheet says 100% Synthetic - ESTER. So, ostensibly, it would contain nothing distilled from crude oil. Its Safety Data Sheet says it contains 1-Decene, trimer, hydrogenated in proportion between 50-100%.

https://d347awuzx0kdse.cloudfront.ne...0617f11f038705

I beleive this compound is considered a polyalphaolefin which is a lab engineered hydrocarbon. The SDS also mentions Distillates (petroleum), hydrotreated heavy paraffinic in proportion between 2.5 and 10%. And it lists Lubricating oils (petroleum), C15-30, hydrotreated neutral oil-based in proportion between 1 and 2.5%. So I would say it is primarily lab engineered and manufactured synthetic oil, with a small amount of petroleum distillates mixed in.

As I noted in post 50, ACDelco is a blend of PAOs and petroleum distillates as well, based on its SDS.

Can you mix them? The PDS for Motul says this, about that: "Can be mixed only with similar quality lubricants"

I'm thinking they are similar quality lubricants and can be mixed, but that just opinion. The PDS does say that the MOTUL product is suitable for use where Pentosin FFL-4 is called for but that is not the same as saying they can be mixed. Pentosin FFL-4 is also the same as Titan FFL-4 and ACDelco DCTF FFL-4.

Its hard to find a complete PDS for the ACDelco product, but if you accept that it is the same as the Fuchs Titan FFL-4 (which I do), there is a PDS for that, and it says " To warrant the perfect functions of the transmission, TITAN FFL-4 must not be blended with any other transmission oils under any circumstances."

https://www.fuchs-lubricants.ro/user...AN%20FFL-4.pdf

So use your own judgment. Folks have mixed Valvoline and residual OEM fluid with no issues.

 

Thanks all, appreciate the insights. I think I will go with Valvoline 888705 given that it’s been used by a lot of other owners.

Has anyone noticed any change in performance or DCT feel as a result of using Valvoline?
And have most people performed a drain and fill? I guess the other option is to do a flush and that would ensure that there isn’t any fluid mixing

 

Sorry if I miss quoted! BUT I'll say, "Can't Use an SDS to Define Equivalent Product."

 

There is no flush procedure for this transmission (not to be confused with the Hydraulic System Flush which does not involve any fluid replacement) and flush should not be attempted, per the tech-link article. If you want to get all of the fluid out (and I am not commenting on whether that is necessary) you need to remove the pan, and you would want to remove the DCT external canister filter cover too. You might try to pump it out, but I do not know if that is feasible.

https://gm-techlink.com/?p=12881

 

Nearly all, if not all, of the fluids that are offered for use in the C8 discuss the importance of friction and friction modifiers in the additive package. This of courses is primarily because the clutches are wet clutches, immersed in the fluid, and the fluid has a function in torque transfer during clutch engagement. Someone brought up the question of whether the friction characteristics of alternative fluids could be different. I think that might very well be true, I do not know. But, what is true is that the transmission adapts as clutch surfaces wear. This can occasionally get out of whack, and sometimes it is resolved by a transmission service fast learn, executed with a scan tool. I can speculate that the transmission would adapt to small variations in friction characteristics of the fluids, if there are any. No one has reported any issues with the Valvoline fluid.

 

I made a distinction about PDS and SDS, but yeah, you are correct when you say that, about both.

The PDS is the manufacturers advertisement sheet where they share what they wish about the product, including recommendations, and the Safety Data Sheet (SDS) which is a government required form and must list ingredients that the EPA thinks may potentially be hazardous. And, you're right - neither one is a perfect way to establish equivalence, unless they mention a recognized specification, such as "meets dexos R". In absence of that, we must guess or accept the manufacturer's statements about applications.

We have no specification for the DCTF that the C8 requires, only product recommendations, and those usually appear in the PDS, or the manufacturers product finder. So when choosing an alternative product, you are relying on the manufacturers reputation and recommendation - and your trust in that.

And similarly, you can't use an SDS to establish equivalence either. They list only ingredients requires by law that are potentially hazardous, and do not list the exact proportions, and I have never seen them mention a product specification. They are useful for determining some of what is in there, but useless for determining equivalence.

 

Part of the problem with friction modifiers is they have competing requirements. On some surfaces (gears, bearings, etc.) you want to have the least amount of friction as possible. On other surfaces (clutches, syncro rings, etc.) you rely on friction for them to function properly. Usually (but not always) you will find out if a fluid is incompatible because of a change in transmission operating characteristics. An example a GL4 transmission fluid that has friction modifiers that allows syncro rings to work properly vs a GL5 fluid that provides high pressure sliding contact protection for hypoid gears. A transaxle that has a limited slip differential with hypoid gears and synchro rings becomes tricky. In older transaxles you would soon find out out if a fluid wasn't compatible due to differential chatter around corners or gears grinding during shifts. However, there were also long term effects of using a GL5 fluid in a transmission designed for GL4 fluid, the brass in the synchro rings was attacked.

Hopefully the fluid manufacturers did their job when recommending their fluid and there aren't any long term effects of using non-ACDelco/Fuchs FFL-4 fluid in a C8 DCT.

 

Indeed. You are probably familiar with this article that someone referenced previously on this forum about MOTULs develop of its high torque DCTF. Its the fluid I discussed in post 72. Essentially true lab engineered synthetic lubricant. What I found interesting about the article (besides it general lack of hard facts) is that it alluded to the trade-offs involved in making fluid that enables the transmission to handle higher torque than the standard Stingray. It did sound a bit like the tradeoff was handling high torque vs protecting the transmission from wear and maybe preserving the shift behavior in street use. It was not especially explicit about the trade offs, only alluding to the fact that there are tradeoffs.

https://www.hotcars.com/emelia-hartf...tul-dct-fluid/

The article discusses, at a high level, some of what was involved in the development of the MOTUL formulation, which included a comparison of the MOTUL fluid and the OEM fluid after use. This sentence stuck out for me, where it is discussing this comparison:

"Motul then tested the breakdown levels of the oil and additives in those samples, trying to find the ideal balance between the car's real-world performance and protecting the transaxle's internal components."

Sounds like a trade off between high performance and protection of the transmission components. The article really does not elaborate on the details of the tradeoffs though.

The product data sheet for this MOTUL promises to deliver on everything - it give "superior transmission response" and "Increased anti wear protection" (not even a hint that there may be a trade-off):

Provides perfect friction level suited to high torque/power engines for transferring maximum power to the wheels.
- Gives superior transmission response: smooth shift feeling and no torque interruption in-between shifts.
- Improves DCT transmissions flexibility and response at cold and high temperature.
- Keeps consistent viscosity even at extreme temperatures to provide the best protection for all DCT components.
- Provides anti-shudder performance to avoid vibrations on engine flywheel.
- Protects numerous gears, compact and heavily loaded.
- Extends lifetime duration, superior shear stability at high temperature.
- Offers significantly better oxidation resistance than conventional synthetic product.
- Increased anti-wear protection, higher anti-corrosion and anti-foam performance