Diff Oil Change

[panthro]

Planning to change the diff oil on my C63. It says it's been done recently on the service history but I would like to do it again and add some friction modifier as the car is on 86k. I did this with my E46 M3 when there was some very mild low speed grumbling and it cured it.
The oil type is 75W140; the OEM stuff is Castrol:

Castrol TRANSMAX Limited Slip LL 75W-140 Fully Synthetic Hypoid Gear Oil

The UK's largest independent supplier of automotive oils, fluid and parts. We've products to suit any vehicle, from full blown Race / Track weapons, to Daily Drivers looking to save money. Plus FREE expert advice & recommendations - OPIE KNOW OILS

www.opieoils.co.uk

but this stuff has added friction modifier:

Motul Gear Competition 75w-140 Fully Synthetic Racing Transmission & Diff Oil

The UK's largest independent supplier of automotive oils, fluid and parts. We've products to suit any vehicle, from full blown Race / Track weapons, to Daily Drivers looking to save money. Plus FREE expert advice & recommendations - OPIE KNOW OILS

www.opieoils.co.uk

Presumably there should be no issue in changing the OEM oil for this? Any advice from someone more informed than me (@Simon?) would be appreciated!

 

[Simon]

Genuine BMW Differential Gear Oil SAF-XJ+FM - 500ml bottle - E46 M3, E9X M3, E60 M5/M6

Genuine BMW SAF-XJ+FM 75W140 GL-5 gear oil for BMW M differentials with limited-slip. BMW part #83222282583.

www.bimmerworld.com

Thats the BMW fix for noisy diff plates at expense of locking performance, the shudder creates noise as the friction material clamps up (controlled by the ball ramp) SAF-XJ is Transmax Limited Slip LL 75W-140 This already has some FM in but BMW wanted more for noise complaints so the BMW is literally that. I use the standard stuff in my E92.

If you dont need it for noise I would avoid it. Not sure what the differential hardware is on the C63 but assume it needs the MB 235.61 spec?

Interested in why you considering the Motul ?

 

[panthro]

Thanks, I didn't realise that was a BMW specific fix. The only reason I considered the Motul is because of the added friction modifier, but if it's not necessary I'll stick with the Castrol or MB oil. No idea on the hardware of the diff but it's a non S so has the standard LSD not the clever "e-diff".
The car does make a minor grumble when turning a circle at full lock, but I need to investigate further if this is the diff. Hoping it might be a wheel bearing.

 

[Simon]

Might be diff. New fluid worth a try

 

[panthro]

Done some more road testing today. Believe it's the diff as low speed full lock turns make no noise except under load.
Will try new fluid first. Otherwise I'll remove and recondition it.