What Differential Fluid

[gjm120]

I posted this under the transmission / diff fluid change diy thread. That thread was a sticky so i'm thinking it didn't get noticed (or maybe no one cares or knows the answer) so here goes a repeat:


A while back I did a differential fluid change using BMW branded SAF-XO 75W90. Now thinking I might have used the wrong fluid.

In RealOem a different part number is shown for differential oil from 07/2011 onward. I know part numbers can change with no change in the part itself, but, it seems the pre 07/2011 oil is a 75W90 GL-5 spec while the 07/2011 forward is 75W85 GL-4. The viscosity isn't my concern, it's GL-4 vs GL-5, specifically the additive package and the way it attaches itself to surfaces.

(initially dug into this when looking into gearbox oil for my old British motorcycles)

Anybody know anything about this? Those with newer cars, what differential fluid did you use?

I'm not hugely concerned since I don't put on a lot of miles and some gear oils carry both GL-4 and GL-5, but, since BMW decided to change spec in 2011, might be worth investigating.

[Bsan]

Following

[NorthernDancer]

Well for me, Red Line Oils is the place to start.

For my 2008 128 they recommend 75W90 GL-5
For a 2012 128 they recommend 75W85 GL-5

135's use same diff oils as 128's

[Suprgnat]

Originally Posted by gjm120

I posted this under the transmission / diff fluid change diy thread. That thread was a sticky so i'm thinking it didn't get noticed (or maybe no one cares or knows the answer) so here goes a repeat:


A while back I did a differential fluid change using BMW branded SAF-XO 75W90. Now thinking I might have used the wrong fluid.

In RealOem a different part number is shown for differential oil from 07/2011 onward. I know part numbers can change with no change in the part itself, but, it seems the pre 07/2011 oil is a 75W90 GL-5 spec while the 07/2011 forward is 75W85 GL-4. The viscosity isn't my concern, it's GL-4 vs GL-5, specifically the additive package and the way it attaches itself to surfaces.

(initially dug into this when looking into gearbox oil for my old British motorcycles)

Anybody know anything about this? Those with newer cars, what differential fluid did you use?

I'm not hugely concerned since I don't put on a lot of miles and some gear oils carry both GL-4 and GL-5, but, since BMW decided to change spec in 2011, might be worth investigating.

The factory diff fluid is cheap crap so BMW can save a few pennies. I would only use synthetic gear oils derive from the gonad-squeezings of a mature bull sperm whale. I mean, it's a BMW! I don't get why people buy premium vehicles and then put in sh*t for fluids.

[gjm120]

Originally Posted by NorthernDancer

Well for me, Red Line Oils is the place to start.

For my 2008 128 they recommend 75W90 GL-5
For a 2012 128 they recommend 75W85 GL-5

135's use same diff oils as 128's

I think the fluid for 07/2011 on is GL4. That is my concern. On RealOEM there is a different fluid specified for 07/2011 on. Bimmerworld, a pretty knowledgeable vendor, shows GL4 for 2012 on and GL5 for earlier.

Strange thing is the differential part number is the same for all years.

As I mentioned in the OP, there is a difference in the additive package between GL4 and GL5 and how it behaves with certain metals.

[gjm120]

Originally Posted by Suprgnat

The factory diff fluid is cheap crap so BMW can save a few pennies. I would only use synthetic gear oils derive from the gonad-squeezings of a mature bull sperm whale. I mean, it's a BMW! I don't get why people buy premium vehicles and then put in sh*t for fluids.

I put in BMW brand only because i was still under CPO at the time. Didn't want BMW to hire CSI Munich to analyse my fluid in the event of a claim.

[iminhell1]

I will not use anything buy Redline Shockproof.

For my Torsen style MFactory, I found the super lightweight gave me the engagement I was looking for.
Factory open diff, use what you like, it's not going to change anything with engagement.

I don't believe you can use it with a clutched diff though.

[Gray_Panther]

I use redline 75W-90.
Going to be changing the fluid again in about 2k miles. Last time at 30k I used the same fluid.
I wonder what the fluid will look like...

[gjm120]

Originally Posted by Gray_Panther

I use redline 75W-90.
Going to be changing the fluid again in about 2k miles. Last time at 30k I used the same fluid.
I wonder what the fluid will look like...

That one is GL4 according to the Redline PDS. I think your car should have GL5, but, don't take my word on it.

From my understanding of the two specs, I'd rather use GL4 when GL5 is called for instead of the other way around, so probably no issue for you.

[Suprgnat]

Originally Posted by gjm120

That one is GL4 according to the Redline PDS. I think your car should have GL5, but, don't take my word on it.

From my understanding of the two specs, I'd rather use GL4 when GL5 is called for instead of the other way around, so probably no issue for you.

You have too much time on your hands.

[Gray_Panther]

Originally Posted by gjm120

That one is GL4 according to the Redline PDS. I think your car should have GL5, but, don't take my word on it.

From my understanding of the two specs, I'd rather use GL4 when GL5 is called for instead of the other way around, so probably no issue for you.

Whats the difference between gl4 and gl5?

[gjm120]

Originally Posted by Suprgnat

You have too much time on your hands.

Maybe I do, but, it's fun.

I've got 3 old British motorcycles they make lubricant choices a challenge to say the least. (I see you have a 1964 Healey.)

[gjm120]

Originally Posted by Gray_Panther

Whats the difference between gl4 and gl5?

Below is a link explaining the difference. Like I mentioned, I got into this looking at gearbox oil for my old Brit bikes. I think there is a good bit of soft metal in those transmissions.

https://www.widman.biz/uploads/Transaxle_oil.pdf

Still wonder why Bimmerworld shows one spec for up to 07/2011 and the other for after. And why does BMW have a different part number? But the differentials are the same part number for across the years for AT and MT cars, so I think I'll park my concern. It really seems that for a differential, no real problem using one or the other.

Here is Bimmerworld's page with lubricants. If you read the info on the two gear oils, you can see the clear as mud nature of all this.

https://www.bimmerworld.com/Fluids/Driveline-Fluids/


I would guess that the MT fluid should be GL4.

[chris_flies]

I always put Redline 75W-90NS in the stock diff. Now with my DiffsOnline clutch unit I used 75W-110, but I'm switching to Lightweight Shockproof to try and up the engagement with the next change.