DCT transmission fluid service

[Moveitsmikey]

Has anyone on here successfully and accurately done a transmission fluid drain and fill on their DCT trans? I really would like to try and do it myself to save some money from having to take it to the shop. Just curious if it's a PITA filling the gearbox? I know it's temp related and specific to filling but who all has given this a go? Tips and comments I'd appreciate.

[Esteban]

Here's a video about changing the DCT fluid. For the M3, M4, M5, M6, 135i, and 335i. Don't know if you've seen it already. Very informative. Note: he makes a small numbers error (viscosity) on the DCT fluid he uses, but nobody's perfect, and he corrects it on screen.

And a 1ADDICTS thread: (there are probably others)

https://www.1addicts.com/forums/show....php?t=1350274

[zx10guy]

I've been wondering about doing this service. I have almost 89k on my DCT but all daily driving. I've asked two respected Indies and a BMW dealer. All of them said to leave the fluid alone if there is no issue going on with my trans either with shifting or leaks. Not sure if any of you all have been hearing this.

[Moveitsmikey]

Originally Posted by zx10guy

I've been wondering about doing this service. I have almost 89k on my DCT but all daily driving. I've asked two respected Indies and a BMW dealer. All of them said to leave the fluid alone if there is no issue going on with my trans either with shifting or leaks. Not sure if any of you all have been hearing this.

That's a huge misconception and I believe complete total bullshit. I hate how people actually believe fluid can be lifetime which is actually 100k miles.

There is absolutely NOTHING special about bmw transmission fluid, it's only part synthetic to begin with. Regardless of any shop advising against it, if it's under 100k miles I'd say go for it.

Fluid just like engine oil breaks down over time and loses its viscosity. It can't 100% protect the transmission for eternity. Same with engine oil. All fluids have service life.

I'm doing mine based on personal experiences and being a stickler about maint. I'm at 71k miles and I'm sure it's original fluid as I have no documentation otherwise stating.

I suggest you find a different shop...

[zx10guy]

Originally Posted by Moveitsmikey

That's a huge misconception and I believe complete total bullshit. I hate how people actually believe fluid can be lifetime which is actually 100k miles.

There is absolutely NOTHING special about bmw transmission fluid, it's only part synthetic to begin with. Regardless of any shop advising against it, if it's under 100k miles I'd say go for it.

Fluid just like engine oil breaks down over time and loses its viscosity. It can't 100% protect the transmission for eternity. Same with engine oil. All fluids have service life.

I'm doing mine based on personal experiences and being a stickler about maint. I'm at 71k miles and I'm sure it's original fluid as I have no documentation otherwise stating.

I suggest you find a different shop...

I agree that this is counter to what I know about lubricating oil. But again, I got this feedback talking to two respected Indies and an actual BMW dealer. They all said they would do it but said they wouldn't recommend it. I find it hard to believe all of these shops would willing turn down money for service if there wasn't something (however small) to their advice.

[Esteban]

My dealer also says it's lifetime fluid, but with a nod and a wink they tell me that is what they're supposed to say. I will definitely be changing mine sooner rather than later. Especially after watching that video.

[Moveitsmikey]

Originally Posted by zx10guy

I agree that this is counter to what I know about lubricating oil. But again, I got this feedback talking to two respected Indies and an actual BMW dealer. They all said they would do it but said they wouldn't recommend it. I find it hard to believe all of these shops would willing turn down money for service if there wasn't something (however small) to their advice.

I think the reason behind this is so when it does internally fail from lack of viscosity and eventually the fluid becomes like water the fluid starts to burn up in the transmission and becomes toast.

It's a complete dirty scam for them to make more money. Figure a dealer charges 900 to service trans where as a new factory installed transmission is thousands and thousands..

[Moveitsmikey]

Originally Posted by Esteban

My dealer also says it's lifetime fluid, but with a nod and a wink they tell me that is what they're supposed to say. I will definitely be changing mine sooner rather than later. Especially after watching that video.

I have in all my cars. Even high mileage, but with no history and high mileage is way more of a gamble than doing it before 100k mile mark.

[zx10guy]

Well, I'll ask my BMW dealer tech friend what he thinks. He'll give me an honest straight answer. I just haven't recently since he's helped me with a bunch of other things I didn't want to push my luck with his generosity.

[Happy Jose]

The DCT uses a very special and expensive transmission fluid made by Pentosin:

http://www.pentosin.net/f_transmissionfluid.asp

I believe it requires 10 quarts @ $30 per, so just the fluid will cost you $300. Another problem is Pentosin warns about contamination of the new fluid, so a transmission flush is required.

The DIYer won't be able to perform this service. Even BMW might not be set up for it. You'll have to find a specialty transmission shop set up to do it. Good luck with that. BMW figures you'll wreck or get rid of the car before the service is required!

[Moveitsmikey]

Originally Posted by Happy Jose

The DCT uses a very special and expensive transmission fluid made by Pentosin:

http://www.pentosin.net/f_transmissionfluid.asp

I believe it requires 10 quarts @ $30 per, so just the fluid will cost you $300. Another problem is Pentosin warns about contamination of the new fluid, so a transmission flush is required.

The DIYer won't be able to perform this service. Even BMW might not be set up for it. You'll have to find a specialty transmission shop set up to do it. Good luck with that. BMW figures you'll wreck or get rid of the car before the service is required!

I'm not going to use pentosin it's crap fluid to begin with. I'll just have a shop do it and I'm def not going to bmw they already misdiagnosed my car

[HyeWarrior]

Im also interested in this. Every shop I've talked to said its pretty much not worth it, which I found shocking as well.

[Happy Jose]

Did you bother to read what Pentosin said?

[Happy Jose]

Originally Posted by Moveitsmikey

I'm not going to use pentosin it's crap fluid to begin with. I'll just have a shop do it and I'm def not going to bmw they already misdiagnosed my car

You are demented. Pentosin is the original fill in the DCT, and it is a very high quality oil. Your shop will likely royally screw up your transmission!

[Moveitsmikey]

Originally Posted by Happy Jose

You are demented. Pentosin is the original fill in the DCT, and it is a very high quality oil. Your shop will likely royally screw up your transmission!

Lmao not even close. That's just overpriced partial synthetic fluid with low viscosity. I do my research before just putting in ANY type of fluid...

[Moveitsmikey]

Originally Posted by Happy Jose

Did you bother to read what Pentosin said?

Yes without even a pdf technical bulletin on the properties of the fluid. 🤦*♂️

[Esteban]

Originally Posted by HyeWarrior

Im also interested in this. Every shop I've talked to said its pretty much not worth it, which I found shocking as well.

Maybe you should show them the video above with the dirty DCT fluid at 30k miles. Wonder if they would think it's worth it then? Besides, don't they want the business?

[tock172]

I paid for new fluid when I had my DCT leak fixed and it wasn't cheap. From my understanding, they were just going to pour the old fluid back in. I'm not sure about the detailed specifics of the service procedure, but at least I'm running fresh fluid.

The idea of not changing the fluid after a certain number of miles applies to conventional torque converter automatic transmissions. Some shops will not touch them once they've covered 80 to 100k miles on the original fluid that BMW branded as Lifetime. I did it anyway on a previous automatic of mine and never had problems. I opted for a simple drain and refill on the conventional torque converter automatic as opposed to a flush which could dislodge particles in the valve body and render the car immovable.

I don't think any of that sentiment applies to DCT. It's a fundamentally different setup. The Lifetime thing I take with a grain of salt. Change the fluid if you want peace of mind.

As far as fluid is concerned, Pentosin is the factory fill from my understanding. Over the last few years though, there are number of alternatives from popular manufacturers. Valvoline, Amsoil, Liqui Moly and several others all make a DCT fluid.

[Gangplank]

I suppose my question is are there many higher mileage DCTs out there? There has to be some 3 series well over 100k by now?

[Moveitsmikey]

Originally Posted by Gangplank

I suppose my question is are there many higher mileage DCTs out there? There has to be some 3 series well over 100k by now?

I know of a 335i with 150k unsure of if it's original fluid though. Peaks my concern now that you mention it.

Also just because a fluid may go 100k moles or kore shouldn't mean to leave it either.

The only circumstance I would not change is if it was bought as 100k plus car with no history of it being done.

At that point you're risking it. But I highly doubt changing fluid before 100k is going to make anything worse.

[Moveitsmikey]

Originally Posted by tock172

I paid for new fluid when I had my DCT leak fixed and it wasn't cheap. From my understanding, they were just going to pour the old fluid back in. I'm not sure about the detailed specifics of the service procedure, but at least I'm running fresh fluid.

The idea of not changing the fluid after a certain number of miles applies to conventional torque converter automatic transmissions. Some shops will not touch them once they've covered 80 to 100k miles on the original fluid that BMW branded as Lifetime. I did it anyway on a previous automatic of mine and never had problems. I opted for a simple drain and refill on the conventional torque converter automatic as opposed to a flush which could dislodge particles in the valve body and render the car immovable.

I don't think any of that sentiment applies to DCT. It's a fundamentally different setup. The Lifetime thing I take with a grain of salt. Change the fluid if you want peace of mind.

As far as fluid is concerned, Pentosin is the factory fill from my understanding. Over the last few years though, there are number of alternatives from popular manufacturers. Valvoline, Amsoil, Liqui Moly and several others all make a DCT fluid.

Yeah it's the factory fill basically with bmw branded on the bottle there is no difference. I'm at die hard Amsoil guy so I'm going to use the Amsoil DCT fluid which has a very solid 171 viscosity index at operating temp. The higher the viscosity the better the fluid strength which means fluid lasts longer and protects against heat. Heat is a number one killer of transmissions.

[Moveitsmikey]

Originally Posted by tock172

I paid for new fluid when I had my DCT leak fixed and it wasn't cheap. From my understanding, they were just going to pour the old fluid back in. I'm not sure about the detailed specifics of the service procedure, but at least I'm running fresh fluid.

The idea of not changing the fluid after a certain number of miles applies to conventional torque converter automatic transmissions. Some shops will not touch them once they've covered 80 to 100k miles on the original fluid that BMW branded as Lifetime. I did it anyway on a previous automatic of mine and never had problems. I opted for a simple drain and refill on the conventional torque converter automatic as opposed to a flush which could dislodge particles in the valve body and render the car immovable.

I don't think any of that sentiment applies to DCT. It's a fundamentally different setup. The Lifetime thing I take with a grain of salt. Change the fluid if you want peace of mind.

As far as fluid is concerned, Pentosin is the factory fill from my understanding. Over the last few years though, there are number of alternatives from popular manufacturers. Valvoline, Amsoil, Liqui Moly and several others all make a DCT fluid.

Yeah it's the factory fill basically with bmw branded on the bottle there is no difference. I'm at die hard Amsoil guy so I'm going to use the Amsoil DCT fluid which has a very solid 171 viscosity index at operating temp. The higher the viscosity the better the fluid strength which means fluid lasts longer and protects against heat. Heat is a number one killer of transmissions.