BMW 228i open differential fluid.

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Rear wheel drive automatic, I plan to change the fluid out while I’m doing a ATF fluid change. It’s at 60k miles and sees track use.

Little confused how much and what type of fluid. I read not to mix GL4 and GL5 fluid, not sure which the OEM fluid is but it sure costs a lot. I was thinking redline 75w85?
 
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Rear wheel drive automatic, I plan to change the fluid out while I’m doing a ATF fluid change. It’s at 60k miles and sees track use.

Little confused how much and what type of fluid. I read not to mix GL4 and GL5 fluid, not sure which the OEM fluid is but it sure costs a lot. I was thinking redline 75w85?
What does Redline recommends?
 

FlyPenFly

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Oh yeah I forgot their website has that,

75W90 GL-5 GEAR OIL​


Guess I’ll go for that?

 
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Rear wheel drive automatic, I plan to change the fluid out while I’m doing a ATF fluid change. It’s at 60k miles and sees track use.

Little confused how much and what type of fluid. I read not to mix GL4 and GL5 fluid, not sure which the OEM fluid is but it sure costs a lot. I was thinking redline 75w85?
Factory fluid is 75W85 GL4. Not sure why BMW uses GL4. If hitting the track, just get some Redline 75W90 GL5. Takes almost exactly 1L. Get 2L just to be safe. Don’t forget to get a new fill plug, single use.
 
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I'd suggest using a magnetic drain plug and either Castrol Syntrax Long Life 75W-90
= Castrol Transmax Axle Long Life 75W-90 (ZF approvals and explicitely recommended
or supposed to be even approved for BMW) or Redline 75W-90, all GL-5. Whichever is
easiest available. Personally I'd change it annually if it sees some track use. Same with
ATF.

 

FlyPenFly

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Huh, do you think axle oil really needs to be replaced that frequently when it’s just a simple open diff?

Any reason to go with Castrol vs Redline besides $10?
 
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Yes, any lube of the entire drivetrain is highly strained on track. All your
fluid's temperaturs are raised, so the fluids are thinner than on regular
driving and protection mostly relies on AW additives. Stock diffs don't
have oil pumps and filters, so removing wear particles is accomplished
by magnets and frequent oil changes only.
Because Castrol is likely the factory fill, but I have just a little preference
for Castrol. Redline is certainly appropriate as well. That said, in this case
cheaper doesen't necessarily mean worse. That's why I said "whichever is
easiest available."
 
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I'd suggest using a magnetic drain plug and either Castrol Syntrax Long Life 75W-90
= Castrol Transmax Axle Long Life 75W-90 (ZF approvals and explicitely recommended
or supposed to be even approved for BMW) or Redline 75W-90, all GL-5. Whichever is
easiest available. Personally I'd change it annually if it sees some track use. Same with
ATF.

All good except they don’t have a drain plug. ;)
 
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I should have known better. While preferably a magnetic plug is used
in the drain location I'd simply use use one as a fill plug in this case.
 
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