[JayD]

So from what I read, the correct part # for the diff fluid is
83222447362. supposedly this is a GL-5 75W-80 weight oil.

Looking at 3rd party suppliers like Motul competition gear oil. This is a 75W-140. oil. That is a big difference from the OEM weight. Is the OEM part # correct? Does the M2 diff take a different weight than the M3/M4?? not sure if any issues would arise running 75W-140

any info would be helpful.

thanks
Jay

[JustinHEMI]

That's the gist of what I was getting at in the following thread. I was surprised what I found when searching the part number vs what was the spec for my F87 rear end.

I felt better that everyone else was getting a similar part number, but I agree, there's still some questions about what's going in. BUT, if it's what they're calling for, I'm satisfied from a warranty perspective.

https://g87.bimmerpost.com/forums/sh....php?t=2020531

[DSTR]

First M-Service yesterday at exactly 2000km here in Germany. This is the BMW Diff fluid used by my dealer. I took a few pics of the service in progress.

[kyrix1st]

Great question.

It isn't uncommon to go higher viscosity depending on your vehicle usage. Going from 0W30 to 5W40 or 70W80 to 75W140 WILL NOT hurt your vehicle. If the vehicle is occasionally tracked and under warranty, I recommend using BMW's motorsport 75W140. (Note that F82 M4 had the exact same differential as that of G87, but had 75W140 for maximum protection)
https://www.bimmerworld.com/Fluids/D...222365988.html

For my moderate track/street usage, I use Motul X-cess Gen2 5W40 and Motul competition 75W140. I use the latter product on all my M3s from E36 to F82, never had an issue.

[KC87ZB]

Originally Posted by kyrix1st

Great question.

It isn't uncommon to go higher viscosity depending on your vehicle usage. Going from 0W30 to 5W40 or 70W80 to 75W140 WILL NOT hurt your vehicle. If the vehicle is occasionally tracked and under warranty, I recommend using BMW's motorsport 75W140. (Note that F82 M4 had the exact same differential as that of G87, but had 75W140 for maximum protection)


For my moderate track/street usage, I use Motul X-cess Gen2 5W40 and Motul competition 75W140. I use the latter product on all my M3s from E36 to F82, never had an issue.

Are you sure the F82 had the same variable slip differential that is currently available on the G8x models? I would expect that the variable slip capability might bring a higher level of stress on the lubricant and higher viscosities might not provide the correct amount of shear in a variable limited slip application.

[kyrix1st]

Originally Posted by KC87ZB

Are you sure the F82 had the same variable slip differential that is currently available on the G8x models? I would expect that the variable slip capability might bring a higher level of stress on the lubricant and higher viscosities might not provide the correct amount of shear in a variable limited slip application.

They both use GKN e-diff in 215mm case housing.
F82 M4:

G87 M2:


I have reasonable suspicion as to why lighter weight was used on G8x: to improve fuel economy, allow more rear braking to emulate locking differential effect and subsequently use less differential locking. Additionally, in 4WD application, rear differential doesn't see as much load as in pure RWD, so this specification was possibly carried from G82 xDrive.

I drive with TC fully off on all my M cars on a track, so I don't let the rear brakes engage for limited slip application. This naturally means more diff usage, and heavier weight makes sense because I'm letting the internal clutches do all the work.

[chris719]

We really don't know what internal changes have been made, but I still tend to believe you are correct here that the thicker fluid will be safe.

[chris719]

Originally Posted by E90convert

Having developed axles with limited slip differentials, and reviewed benchmarking teardown and test data on the F8X and F10 M5 differentials, would use the genuine 75w-80. Aside the from the viscosity, the additive package may be more tuned to a different clutch pack material. The lockup calibration and wear characteristics may be heavily influenced by these additives and this viscosity. Remember that BMW tested this car for durability and is providing a warranty with that oil in the differential.

The G8X uses the same differential as the F10 M5 and X5/6M. These cars also run 75w-80.

Both the F10 M5 and F8x specify MSP/A (EU) or Castrol SAF-XJ (NA) 75W-140 for that diff. I would assume the 75W-80 started with the F90 or X models.

[E90convert]

Originally Posted by chris719

It's odd that the F8x, which was released after F10 M5, would specify the MSP/A or Castrol SAF-XJ 75W-140 for the same diff.

I’m struggling to think of a legit technical reason why the F8X uses a much heavier oil while M5/X5/6 use a relatively light axle oil.

I’ve looked at teardown and test data for each and their isn’t much difference between the two. Maybe I’ll take a closer look tomorrow at the data.

[chris719]

Originally Posted by E90convert

I’m struggling to think of a legit technical reason why the F8X uses a much heavier oil while M5/X5/6 use a relatively light axle oil.

I’ve looked at teardown and test data for each and their isn’t much difference between the two. Maybe I’ll take a closer look tomorrow at the data.

I ninja edited my reply after you started replying it seems, sorry. The F10 actually did come with the heavier oil also. The F90 is the first M5 that went to the lower visc oil. I assume it's just like the S55, which was designed with 3.5 HTHS oils as the target and back-specified as testing with the FE oil showed no issues meeting their targets.

The only reason I could think of to keep F8x on that oil otherwise is that perhaps BMW believed a higher percentage of owners would track the car, leading to higher temps.

[E90convert]

Originally Posted by chris719

I ninja edited my reply after you started replying it seems, sorry. The F10 actually did come with the heavier oil also. The F90 is the first M5 that went to the lower visc oil. I assume it's just like the S55, which was designed with 3.5 HTHS oils as the target and back-specified as testing with the FE oil showed no issues meeting their targets.

Tomorrow I’ll double check the oil part number we used in our benchmarking testing.

[E90convert]

Originally Posted by E90convert

Tomorrow I’ll double check the oil part number we used in our benchmarking testing.

Just looked... we have the 2018 M5 rear axle benchmarked, the oil is 83 22 2 447 362 which is 75w-80... and this is for the F90!

[chris719]

Originally Posted by E90convert

Just looked... we have the 2018 M5 rear axle benchmarked, the oil is 83 22 2 447 362 which is 75w-80... and this is for the F90!

That makes sense, since F90 was after the F10 and F8x.