Manual Transmission Fluid (Thread 2.1)

[jayjaya29]

He mentions there's no copper corrosion difference. Synchros in the 420G are brass.

Yellow metal = copper and brass

[Zack]

Royal purple synchromax is really good, butter smooth shifting!

[ac427]

Royal purple synchromax is really good, butter smooth shifting!

How old was the oil before you changed to Royal Purple?

Have you run any other gearbox oils?

[Tbonem3]

Royal purple synchromax is really good, butter smooth shifting!

RP mention in 2026

[ac427]

I think i have tried them all over the years.

The RP didn't was anything great. I found new MTF-LT2 to be as good. The Redline stuff has been really good though. Still any new oil is going to be better than old oil.

[Obioban]

RP mention in 2026

lol, exactly. Thought we were finally over it.

[maw1124]

lol, exactly. Thought we were finally over it

🤣🤣🤣

I had forgotten all about them.

maw

[chris719]

He mentions there's no copper corrosion difference. Synchros in the 420G are brass.

Brass is copper and zinc.

[CrookedCommie]

Correct, my point was that the video linked only mentioned copper corrosion difference, not brass or zinc, which is dependent on the EP additive they have. I haven't messed up a 420G or a ZF320 running GL-5 yet, but I have messed up two running Redline D4 ATF, even though they claim it's GL-4 compatible. So use whatever fluid you want, but be aware of the risks.

[Cronenberged]

Finally changed the transmission fluid in my new M3 after about a year of ownership and roughly 7,500 miles.

I went down the rabbit hole researching this thread and everything related to fluid options. While gear oil doesn’t technically have a strict shelf life, storage conditions absolutely matter. The last two bottles of BMW MT-LT-2 I received in 2023 for my previous M3 were sun-faded and had a 2012 production date.

I decided to go with Amsoil Synchromesh, it’s a 5W-30 gear oil - don’t panic. Gear oil and engine oil use different rating systems; in gear oil terms, it’s comparable to a 75W-90, which is essentially what BMW supplies now.

After two weeks of use, including cold mornings around 26°F (and slightly colder with wind chill), shifts have been very smooth. No notchiness or crunching so far. I’ll report back after a few months, but at this point I’m happy with it - though that could just be the “fresh fluid” effect.

For what it’s worth, I’m one of three people I personally know running this fluid without any issues and one having been running it for 7 years.

[0-60motorsports]

Finally changed the transmission fluid in my new M3 after about a year of ownership and roughly 7,500 miles.

I went down the rabbit hole researching this thread and everything related to fluid options. While gear oil doesn’t technically have a strict shelf life, storage conditions absolutely matter. The last two bottles of BMW MT-LT-2 I received in 2023 for my previous M3 were sun-faded and had a 2012 production date.

I decided to go with Amsoil Synchromesh, it’s a 5W-30 gear oil - don’t panic. Gear oil and engine oil use different rating systems; in gear oil terms, it’s comparable to a 75W-90, which is essentially what BMW supplies now.

After two weeks of use, including cold mornings around 26°F (and slightly colder with wind chill), shifts have been very smooth. No notchiness or crunching so far. I’ll report back after a few months, but at this point I’m happy with it - though that could just be the “fresh fluid” effect.

For what it’s worth, I’m one of three people I personally know running this fluid without any issues and one having been running it for 7 years.

Thats great to know thanks for the update.

[D-O]

I am going to try the Motul this summer. I am guessing it will be less than great when cold, but the summer track days here in Atlanta are tough on all the fluids and I am hoping it will work well on those hot track days.

[Cronenberged]

I am going to try the Motul this summer. I am guessing it will be less than great when cold, but the summer track days here in Atlanta are tough on all the fluids and I am hoping it will work well on those hot track days.

Looking forward to your review

[duperdog]

Has anyone every tried 1/2 MTF and 1/2 ATF?

Yes. Been pretty happy with it. Smoothed out the 1-2 shift noticably. I also use this mix in my 128i.

[dog2bert]

Yes. Been pretty happy with it. Smoothed out the 1-2 shift noticably. I also use this mix in my 128i.

Which MTF and ATF do you use?