[Richardo]

Well my '07 335i is due for the 2 year brake fluid change, and I'm thinking of having the automatic transmission fluid changed too. I only have about 20,000 miles on the car, but since I do occassional autocrossing, I think it might be beneficial. I'm interested in everyone's opinion (especially if you're an engineer ). Thanks for your help.

[M_M]

it won't harm anything... i just changed mine @ 6200 miles/2 years.

[Richardo]

Thanks M_M -- I'm thinking the same thing.

[darkphantom]

13k miles on my 07....if I don't sell it, i'll go a similar route.

[bimmer_335]

do you pay for transmission flush or is it covered under the 50k maintenance.

[cvc 22349a]

You pay for it. BMW says it's a lifetime fill. Good idea to change it if you're going to keep the car past 100k. BMW uses Shell M-1375.4 trans fluid. BMW P/N 83-22-01-42-516

[hun77777]

$508 for tranny oil?

[yoyeewee]

I wouldn't change it. I talked to a BMW master tech and he said it's actually more harmful to change it early. His experience is that over time, the fluid in your transmission has adapted to the internal environment. When you flush the fluid and fill it with new fluid, it may make the internals not work in harmony therefore causing pre-mature failure. His advice makes sense. Why else would BMW NOT recommend changing the transmission fluid early?

[who's ur daddy?]

Originally Posted by yoyeewee

Why else would BMW NOT recommend changing the transmission fluid early?

Because there were previous complaints about how expensive BMW was to maintain. Then BMW launched an initiative to reduce the maintenance costs to owners.

Some actuarial monkey in accounting was likely asked to do an analysis of cost to replace trannies during warranty period vs. cost to BMW of doing the flush. And said monkey determined that it was cheaper to just slap a lifetime tag than to pay the costs of fluid changes.

All of the above is conspiracy theory, but I am certain that BMW has not changed the laws of physics.

[RipsE92]

Originally Posted by who's ur daddy?

Because there were previous complaints about how expensive BMW was to maintain. Then BMW launched an initiative to reduce the maintenance costs to owners.

Some actuarial monkey in accounting was likely asked to do an analysis of cost to replace trannies during warranty period vs. cost to BMW of doing the flush. And said monkey determined that it was cheaper to just slap a lifetime tag than to pay the costs of fluid changes.

All of the above is conspiracy theory, but I am certain that BMW has not changed the laws of physics.

+1

And BMW also tells you not to change your motor oil in a turbocharged car for 15k miles. I do mine every 5k.

[Kevin@AKMotorwerk]

Originally Posted by yoyeewee

I wouldn't change it. I talked to a BMW master tech and he said it's actually more harmful to change it early. His experience is that over time, the fluid in your transmission has adapted to the internal environment. When you flush the fluid and fill it with new fluid, it may make the internals not work in harmony therefore causing pre-mature failure. His advice makes sense. Why else would BMW NOT recommend changing the transmission fluid early?

that master tech needs to use some common sense. thats like saying you will wear your engine out early if you change your oil weekly.

back in the day it was a wise mans tale that if your transmission oil wasnt changed for a long time then you shouldnt change it because the dirt actually held everything together.

todays transmissions are electronically shifted and controlled, not like back in the day when the transmission was basically a stand alone set up. you can change your trans fluid daily if you want, its not going to hurt anything. trans fluid contains detergents that will keep your friction disks clean of clutch dust and glazing. over time that detergent breaks down and stops keeping everything as clean, so more frequent fluid changes will keep the trans much cleaner and last longer

[2wheelsrbetter]

+1. trans fluid that adapts to your trans... does it have dna? will it spawn new fluid molecules to form a 7th gear if needed? if the fluid's lifetime, then maybe there's less chance of issue by leaving it be - i.e. human error when a service tech changes it and messes something up. but hard for me to believe there's some sort of relationship built between fluid and trans that will be disrupted if new fluid's introduced. which would then be like having an ex-gf lurking in my torque converter. i'm for changing it.

[e90fanatic]

while we are on this subject about changing oil....does "low mile oil service" done at dealerships not recorded? I just brought my car in yesterday and they said the car never had oil changed since 2007. I bought my car in Nov 2007 and remember that I asked them to do the 1 year oil service Oct 2008 (but somehow the computer said the next oil change is Nov 2009 - 2 years from the delivery date). Now I'm concerned that they didn't do what they were supposed to do??

[uberschnell]

Bimmer Magazine talks about this all the time. HISTORY has shown that not changing the Trans oil on a BMW with Auto greatly increases the likelihood of premature failure. The standard recommendation has been 50K.

[bimmer_335]

Originally Posted by e90fanatic

I bought my car in Nov 2007 and remember that I asked them to do the 1 year oil service Oct 2008 (but somehow the computer said the next oil change is Nov 2009 - 2 years from the delivery date). Now I'm concerned that they didn't do what they were supposed to do??

you got that right... they never changed the oil... they should be doing it after 1 yr or 15k miles... whatever comes first.

I must be living in lala land if I was to believe there is any oil (sythetic or not) that will last forever. I would think if they are saying this oil will last forever, then they need to back that up with atleast 100k warranty... lol... which they dont. I will have mine done just before the 50k warranty runs out... may be around 45k miles just in case a service tech messes somthing up.

[yoyeewee]

I agree with what you guys said and that's what I originally thought to.

But this is coming from a BMW Master Tech. Why would he advise against it?

Are there any engineers or technicians on this forum who can shed some light on this subject?

[roozie2001]

changin tranny fluid at 20k is ridiculous and completely unnecessary. i guess some of u guys have money to throw away. more power to you. Hope i can be that care free someday. As for me im all for a balance of keeping my car running well and saving my money. 7500miles for an oil change, 45-50k for tranny fluid and 93 shell octaine and im good to go.

[Octet]

Like engine oil, all depends on driving habits, city versus highway driving...

I could see changing at 25-35 thousand miles myself.

[Chowbow]

You may have a hard time convincing the dealer to do it actually. On our E36 with an auto, they wouldn't do it. They're saying no to money because it was a lifetime fill. I knew they wouldn't do it on my E90 (manual) so I DIY'd it. 30k miles later on my car and the old fluid was significantly dirtier, but did not have any burnt smell in there. An auto tranny will tax the fluid a lot more though and I would think by 50k, the fluid should be changed. The fluid itself is expensive though.

[Richardo]

Everyone,

Thanks for the comments -- they were all very helpful. I'm planning to keep the vehicle for a long time, so I'll probably end up getting it changed before the 50K mark. However, I think I'll hold off until I've put another 5K to 10K miles on it.

Thanks again.

[shifterboy45]

ok while everyone is throwing their cake around the room, let me add the icing ...

it is sad but true that there is a lifetime interval for the fluid.... that said it was not within the bound of accounting or anyone in BMW making the call for extending (or rather eliminating) the transmission service interval ---
NEWS FLASH -- that came directly from the transmission manufacturer. BMW never has built there own transmissions -- ZF(early autos) and GM (late autos) supply the transmissions. so you may want to write you local transmission congressman and have them amend that policy.

just think about it, these transmission intervals have been around since 1993, long before the e90 platform could take shape. poor E36/38/39 owners had to endure the same thing i suspect.

and for the record, not every transmission survives a transmission oil change -- there are plenty of stories of the old ZFs giving up the ghost on a fresh fill. i have heard nothing in regards to the state of the new GMs so to say its a bad thing for you to service your trans, id be lying to you. but i just had to say BMW was not involved in the service interval process in the case of transmissions.

[Richardo]

It's an excellent point, thanks for posting it.