Diff oil recommendation.

[KitTheRam]

Hello.

Thinking about changing the diff oil in my Touring as it’s never been done during my ownership and I hope it may make the car a little smoother - it’s a 1995 520i diff (running off a 525i engine).

I am UK based and was thinking: https://www.opieoils.co.uk/p-737-cas...xle-fluid.aspx

Any recommendations will be appreciated.

Thanks in advance.


Kit

[shogun]

75W-90 for non limited slip diff, in case your car has limited slip diff, Castrol Syntrax Limited Slip 75W-140 Axle Fluid for Limited Slip Differentials

[KitTheRam]

Thanks. I doubt my 520i came with a limited slip diff! Nothing mentioned on the vin checker and no traction control / winter pack as far as I know!

I have opted for Millers fully synthetic 75w-90 Oil which should do the trick, no idea when it was last changed but I am guessing many, many years ago.

Another question - should I change my gearbox oil? No real issues or noises but I know they are not sealed for life. If so, what is the capacity of a late e34 520i manual gearbox and what oil is recommended? Castrol ATF?

[shogun]

Before you drain the oil from the diff, check/confirm that you can open the oil fill bolt, some are terribly corroded.
for the gearbox use one of the online oil finders, they usually mention the details, if I remember correct: manual gearbox 5/1 Capacity 1,2 litre

[KitTheRam]

Thanks for your advice Shogun.

[Onizukachan]

They were def 3 but as def3 no longer exists, the plainest atf you can find of a good brand. The suggested generic Castro atf or if you have GM atf (vs ford merc fluid which iirc was dex4)