Changing m3 transmission oil is harmful

[Siajoon]

So I decided to do a diff and trans flush on my MT e90 M3 at a reputable Indy shop after checking with a BMW dealer on a quote which was outrageous. During my conversation with an SA he informed me that it’s not good to change the transmission oil because the car gets used to the older oil and putting fresh oil in it can actually cause premature transmission failure. This seems like BS and wanted other people’s input on what this SA told me... makes zero sense to me.

Anyone care to chime in on this?

[roastbeef]

its not true, in most cases.

i've heard a few theories about this though- drain and fill at any mileage is ok. flushing a high mileage transmission has been said to be bad because it unsettles sediment that the transmission "got used to" working with. i actually knew a person that got sold a transmission flush as part of a service, and it took a dump a week later (it wasn't an m3).

common practice would be to drain and fill before the mileage gets too high. that way, there is always newer fluid in there.
i'm dct, and i got the infamous leak at about 30k, so i know the fluid in there is just getting to 30k miles. i was planning on doing a fancy slonik pan soon anyways.

[Properstyle]

This is more so common on automatic cars with tq converters.

[doogee]

Haha transmissions do not get "used" to what fluid they have. A transmission is not capable of knowing this.

You should most definitely change it, and find a new mechanic

[inTgr8r]

^whs

[GORDON.M3]

It's a load of shit. Change your oil, nothing is lifetime.

[Properstyle]

I think most of you are not aware of what the SA was referring too. The SA was confused in that we are talking about a DCT but it is pretty common knowledge that it is risky to change out all the fluid on a high milage standard Automatic car that uses a tq convertor. This is why Benz has a trans flush services as early as 40k miles as flushing fluid after 80k risk slippage.

[Siajoon]

Originally Posted by Properstyle

I think most of you are not aware of what the SA was referring too. The SA was confused in that we are talking about a DCT but it is pretty common knowledge that it is risky to change out all the fluid on a high milage standard Automatic car that uses a tq convertor. This is why Benz has a trans flush services as early as 40k miles as flushing fluid after 80k risk slippage.

I made sure the SA knew I was talking about my MT M3 but maybe he overheard that part and might have thought I was talking about a general Auto transmission? Who knows.

[rantarM3]

Yes, it is harmful...for your wallet.

[timothy2001]

There is merit to this claim on vehicles with Torque Converters but only if the fluid change is way overdue in my experience.

Based on my experience as a Service Manager years ago in a GM franchised dealership, change the transmission on high mileage older GM cars where it has not been changed before at your own risk.

Maybe this SA does not have the BMW experience to draw on and is using his prior experience.

So, maybe this is another reason to have a 6mt. Heheheheheheh.

[tlow98]

Your transmission would feel a lot better if it got used to me shifting it...on a daily basis.

Please send car for results. Results take approx 3 years.

Results are guaranteed or 1/10 of your depreciated value will be 30% refunded.

[motion732]

This sounds like some bs

[schnell1982]

Originally Posted by Siajoon

So I decided to do a diff and trans flush on my MT e90 M3 at a reputable Indy shop after checking with a BMW dealer on a quote which was outrageous. During my conversation with an SA he informed me that it’s not good to change the transmission oil because the car gets used to the older oil and putting fresh oil in it can actually cause premature transmission failure. This seems like BS and wanted other people’s input on what this SA told me... makes zero sense to me.

Anyone care to chime in on this?

That would be true on a higher mileage transmission that has not had regular servicing.
BMW to advertise "lifetime fluid" is pure BS
If a higher mileage transmission that has not had a service and it at 130K miles for example and during the drain there is some material from the clutch for example that is not noticed.. with the fresh fluid added it is possible to introduce abnormal shift characteristics. Usually is the valve body reacting to the newer fluid which is in fact thicker then thinned out oil that has been in the transmission for 10 years / 130K miles.
So its possible but the topic conversation can be misunderstood at times based on the scenario.

[pbonsalb]

It’s just unfortunate when the topic is misunderstood by the BMW service advisors supposedly there to help you.

[Siajoon]

Originally Posted by pbonsalb

It’s just unfortunate when the topic is misunderstood by the BMW service advisors supposedly there to help you.

yup... its true. But it happens quite often. Few service advisers are knowledgeable from my experience. For the most part they just deal with basic day to day operations.

[dparm]

Originally Posted by pbonsalb

It’s just unfortunate when the topic is misunderstood by the BMW service advisors supposedly there to help you.

Service advisors are salespeople. They are not mechanics.

[timothy2001]

Originally Posted by dparm

Service advisors are salespeople. They are not mechanics.

Not too many people know this but you are absolutely correct. Some states however make it illegal to compensate service writers based on sales results but there are plenty of ways around that.

Knowledge is power so be it an independent or franchises dealership it’s best to be equipped before going in.

[dparm]

Originally Posted by timothy2001

Not too many people know this but you are absolutely correct. Some states however make it illegal to compensate service writers based on sales results but there are plenty of ways around that.

Knowledge is power so be it an independent or franchises dealership it’s best to be equipped before going in.

There was just a court case for this, actually. It was determined that service advisors were not eligible for overtime pay (like the mechanics) because they were legally classified as salespeople.

[admranger]

Ask him if you should change your engine oil b/c your engine is used to the oil that is in it.

Unreal.

[BanjoPaterson]

Originally Posted by Siajoon

So I decided to do a diff and trans flush on my MT e90 M3 at a reputable Indy shop after checking with a BMW dealer on a quote which was outrageous. During my conversation with an SA he informed me that it’s not good to change the transmission oil because the car gets used to the older oil and putting fresh oil in it can actually cause premature transmission failure. This seems like BS and wanted other people’s input on what this SA told me... makes zero sense to me.

Anyone care to chime in on this?

OK - since this is the internet and I'm the *least* mechanically qualified person in this forum, that means I can answer this question with full authority -- safe in the knowledge that the Dunning-Kruger Effect will protect my ego.

From what I understand is if an automatic transmission hasn't had regular changes then, over mileage and time, a sludge buildup occurs. A sudden transmission fluid change will usually replace about half the fluid and the fresh fluid releases particles of old build-up. These circulate throughout the transmission leading to slipping gears, pressure drops, overheating, cats and dogs marrying, and eventually complete failure. One touted solution is to change the fluid two or three times in short period, e.g. weeks. A better solution is not to believe the "sealed for life" rubbish -- although I believe that mantra has been lost to BMW and Mercedes recently -- and change the ATF regularly before buildup occurs. Or not at all and takes yer chances.

The E92 M3 is a dual clutch manual... not an automatic. It doesn't use a torque converter but two clutches instead. I believe the purpose of the DCT oil is to cool the transmission and so I'd recommend changing it regularly since it will heat up and cool down, thereby (over time) affecting the oil's properties. However, not remembering to do this this isn't usually a problem with the E9x M3s since it has a stupidly designed DCT oil pan made of plastic. This oil pan plus the gasket will -- generally --- begin to leak and require a replacement anyway. This is when you're forced to change the DCT oil -- as happened to me after about 30,000 miles.

So. My naive understanding of the situation.

** EDIT - just read that the OP was a MT, not DCT. Same argument re heating and cooling affecting the oil.