[dylansauers3]

Hey everyone. So I have a 2020 X3 M40i and I am currently at 165,000 miles. “I know it’s a lot” it has driven amazing since I bought it, absolutely not one issue with this car and I love it. Planning on keeping it until it dies. I would like to know what services yall would recommend for it. I’ve read transmission flush but also heard that’s bad idea after 100k. Maybe just a trans fluid change? What would yall recommend I do to this?

[SO8]

The gearbox is allegedly sealed for life .... but in the UK people are getting the oil changed at 60k ish. I can't see as changing it at a mileage over 100k is bad as the oil is going to be struggling. You are only going to potentially increase the life of the transmission surely ?

Impressive mileage btw ! I managed all of 20 ish in my 2019 and sold it last year. Worst motoring decision in my life ... only a faulty boot load cover in 4 years and faultless ...

I am now back in an M240i xdrive which is awesome with the same engine and 4wd but less toys and space sadly.

[dylansauers3]

Originally Posted by SO8

The gearbox is allegedly sealed for life .... but in the UK people are getting the oil changed at 60k ish. I can't see as changing it at a mileage over 100k is bad as the oil is going to be struggling. You are only going to potentially increase the life of the transmission surely ?

Impressive mileage btw ! I managed all of 20 ish in my 2019 and sold it last year. Worst motoring decision in my life ... only a faulty boot load cover in 4 years and faultless ...

I am now back in an M240i xdrive which is awesome with the same engine and 4wd but less toys and space sadly.

Yeah I figured getting the fluid changed would be better for it since it probably is running harder in dirty oil but I’ve been told it could potentially mess it up and to leave it alone. I’ve also read things that say change it every 60k so I’m just torn.
But thanks about the mileage lol it’s definitely the longest lasting bmw I’ve ever owned. Everything is still solid. No creaky noises in the interior nothing.
It actually got stolen a month ago and they obviously drove it like they stole it so I’m just kind worried about the trans/engine

[bouchy]

Transmission oil, crank case, front and rear diff (different P/N, but the same scpecs for front/rear d.),...

[dylansauers3]

Originally Posted by bouchy

Transmission oil, crank case, front and rear diff (different P/N, but the same scpecs for front/rear d.),...

Thank you. I’ve been hearing the same things from tech friends but then I’ve heard changing the trans oil could cause issues after 160k so idk what to think.
I don’t see how changing the dirty oil could cause any issues

[bouchy]

Sudden change of viscosity. In case of engine oil, some people fear dissolving old sediments and immediate failure of an engine. This is not the case, transmission fluid usually contains abrasion of gears, synchromesh, absorbs humidity, gets old with age... I'd recommend a flush with two batches of fluid. Yes, it's rather expensive, but safe. The first batch will flow away any residues of abrasion etc. and won't taint the second batch. Any additive (to flush) will be contained in the final filling, even though it would be drain away.
Drain old - 1st refill - some km of drive (for the fluid/s to get to operating temp) - drain - 2nd refill.

Oh yes, this is also recommended because decent amount of the old fluid will stay in the case with no option to get it out.
Change the filter as well (funny story: 1st time change in certain type of transmission is done by official dealers without transm. oil filter! :O "It's hard to get it out". No wonder some gearboxes have bad reputation: non-smooth, loud. Well, 1st time changer omitted the filter.)