Metal specs in Rear Diff Fluid.

[FrankMstein]

I'm going with AMSOIL SEVERE GEAR 75W-140 when I change in the next two weeks.

[edycol]

Originally Posted by maniz

What's your take on the BMW OEM fluid? I am going to change mine now. Should've done it every 15K miles for peace of mind but never thought of it 'til now. Car has 36K and last change was at the 1,200 mi break-in service.

I do not do hard launches but hard acceleration while rolling (esp. on highway on ramps is pretty regular).

BMW OE fluid is fine. Probably above average.

[SCS55]

Update: 4th flush, 6900 Highway miles on Motul 75W140.
The iron level increased but the mileage sample was more than the others. Actual wear per 1000 went down. No issues, I'll do one more at another 6900 and compare then call it a day

[Fat Goose]

Is the Motul 75w140 competition gear oil discontinued now??

[hellokitty]

Originally Posted by Fat Goose

Is the Motul 75w140 competition gear oil discontinued now??

No, supply chain issues made this gear oil nearly impossible to find anywhere in the US.

[Track/S]

The car has 32,000 km, I change the differential oil every 10,000 km, motul gear competition 75/140





The internal discs are the ones that cause the gray dust dirtying the oil, I don't care.

[Fat Goose]

Originally Posted by hellokitty

No, supply chain issues made this gear oil nearly impossible to find anywhere in the US.

I was able to buy two of a retailer thru ebay but FCP Euro is now showing discontinued vice back ordered.

[FrankMstein]

Amsoil severe gear 75W-100 and 4 track days on it. Nice and quiet still.

[N55Msport]

Update: looks like Motul Gear Competition is working. Latest rear differential analysis shows much better oil wear.

[M4cs_Dan]

Hi,

Planning to change the oil in my diff. Debating on whether going with the Motul Gear Competition 75-140 or the BMW OEM Fluids?

What made you guys change from OEM to the likes of Motul? Are they better than the OEM?

Thanks,

[AlmondJayRoM3]

Originally Posted by M4cs_Dan

Hi,

Planning to change the oil in my diff. Debating on whether going with the Motul Gear Competition 75-140 or the BMW OEM Fluids?

What made you guys change from OEM to the likes of Motul? Are they better than the OEM?

Thanks,

Highly doubt there would be any significant difference between oem and those other brands when it comes to performance or wear in the differential.

I would stick with BMW SAF-XJ, Castrol SAF-XJ, or Castrol Syntrax Limited Slip 75W-140. All three have BMW approval for use in this differential so there is no question about compatibility.

[N55Msport]

Originally Posted by M4cs_Dan

Hi,

Planning to change the oil in my diff. Debating on whether going with the Motul Gear Competition 75-140 or the BMW OEM Fluids?

What made you guys change from OEM to the likes of Motul? Are they better than the OEM?

Thanks,

I went all Motul a year ago oil, brake, gearbox, and decided I might as well get the rear differential too. So, mainly out of simple fiddling. Looking back, I would have stuck with OEM.

[Fat Goose]

Originally Posted by N55Msport

I went all Motul a year ago oil, brake, gearbox, and decided I might as well get the rear differential too. So, mainly out of simple fiddling. Looking back, I would have stuck with OEM.

Why say that? Didn’t your Blackstone reports say otherwise vs going back to OEM?

[N55Msport]

Originally Posted by Fat Goose

Why say that? Didn’t your Blackstone reports say otherwise vs going back to OEM?

I was not clear. I meant to say I should have stayed with OEM Differential Fluid. Running 17,000 miles on the Liqui Moly 75W140 could have damaged it creating all that excess metal. Yes, the reports with Motul are a positive trend.

[Fat Goose]

I have Motul in there, I stay away from the Liqui Moly stuff.

[E90convert]

200ppm on iron on a rear axle is perfectly fine for 17k. I don’t think Liqui Moly 75w-140 did any damage to your diff. Is it the optimal oil for it? No, the diff was design and validated using SAF-XJ. There are certainly other oils that may produce less contact wear, but perhaps they have not balanced the friction additives needed for the e-LSD to work as designed and calibrated. And wear reduction may be insignificant. In any case, no lube is gonna change gear bending fatigue or bearing sub-surface fatigue. They are typical design failure modes for rear axles.