I counted on that when I changed my diff fluid. Didn't catch the distinction until after I did it.
Redline 75w85 for BMW
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All it says on the BMW bottle is “75w”
MolaKule
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And that means nothing in terms of the actual viscosity, which is why an oil sampling must be done.
If I were to make an educated guess, I would say this fluid would most closely match your transfer case fluid:
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I’m also Curious how the redline mt lv fluid can satisfy 70w and 75w
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MolaKule
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I'll give you the same information I gave MightyMouseTech
But here is the catch: A 75WWhat (75WXX??)? A 75W80, a 75W85, or a 75W90???
We need to match the viscosity as close as we can because of the SAE gear lube ranges
could result in 100C viscosities ranging from 6.5 cSt to 23 Cst.
And once we can see the general chemical signature, we can match it up to what is already available.
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I'll give you the same information I gave MightyMouseTech
But here is the catch: A 75WWhat (75WXX??)? A 75W80, a 75W85, or a 75W90???
We need to match the viscosity as close as we can because of the SAE gear lube ranges
could result in 100C viscosities ranging from 6.5 cSt to 23 Cst.
And once we can see the general chemical signature, we can match it up to what is already available.
hmm, ok Mola. Not knowing that, I would have assumed it was a straight 75
MolaKule
Staff member
You're still missing the point:
Look at the 75W block and you will see it has a range of viscosities: https://bobistheoilguy.com/viscosity-charts/
The SAE grade really means nothing as you can have a range of viscosities for any grade so don't let the SAE XXW confuse you. It's the actual viscosity at 100C that is important, because this is where the minimum film thickness of the fluid was targeted in the gear and bearing design.
https://www.redlineoil.com/mt-lv-70w75w is in the middle of the 75W range with a 100C viscosity of 6.5 cSt
Redline said:
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Shell calls it “transmission fluid”. It doesn’t mention “75w”. The BMW bottle, which is the Shell fluids says “SAE 75w”. I don’t know a lot about this, but I can email Redline and see if they can give any useful information.
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My head hurts.
As much as I love Red Line, this calls for strict adherence to factory specs and fluids.
IMHO.
As much as I love Red Line, this calls for strict adherence to factory specs and fluids.
IMHO.
MolaKule
Staff member
Here is the information they will give you:
Like I said, don't get hung up on the SAEXX gear oil stuff and pay particular attention to the Kinematic Viscosity@100C.
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Ok, I understand what you are saying now about the viscosity at 100C. I don't know much about transfer case fluids, so I might stick with the Shell fluid.
If I were to go to Redline 70w/75w Mt-LV, is the Redline's 6.5 vs Shell's 6 viscosity at 100C much of a difference?
Thanks for the good info.
MolaKule
Staff member
The Redline MT- LV would give you a slightly thicker fluid film.
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Thank you Mola! I think I will just use the Shell transfer case fluid, since it does not seem like many people have used the Redline MT-LV for BMW Xdrive transfer case. I would not have any proplem going aftermarket on transmission fluid. But it's still very weird that BMW specs 2 different 75w85s - 1 for front and 1 for rear. I don't know what year this went into effect.
+1Ya, OK. I would just use the Redline 75W90 front and rear (if you want the most protection), or 75W85 GL5 (if fuel economy is also a factor) and be done with it. I use all BMW fluids because, well, I have a gallon or so of each under my bench for free. They are good fluids though. No problem changing the viscosities in the diffs. The transfer case is a completely different animal though.
I have no idea why BMW calls for a GL4 in the rear diff, does seem odd.
Genuine BMW 75W85 G1 GL-4 Rear Axle Gear Oil - 500mL Bottle
Genuine BMW 75W85 GL-4 synthetic gear oil for 2012+ differentials without limited-slipwww.bimmerworld.com
Redline in the diffs will be perfectly fine, and OEM fluid for the T-case.
It was changed late 2011.
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Interesting. Redline told me 2016+ models went 75w85
There are at least some 75W-85 gear oils that say both 'transfer cases and differentials'. Shouldn't these hence fulfill the needs of both the diffs front and rear and the transfer case?
www.ravenol.de
www.ravenol.de
RAVENOL MTF-1 SAE 75W-85
RAVENOL MTF-1 SAE 75W-85 is a PAO based full synthetic, low-viscosity transmission oil for special manual transmissions, transfer cases and differential ge...
www.ravenol.de
RAVENOL DGL SAE 75W-85 GL-5 LS
RAVENOL DGL SAE 75W-85 GL-5 LS is full synthetic multi-grade hypoid transmission oil of API GL-5 power class with “limited slip” properties for manual tran...
www.ravenol.de
MolaKule
Staff member
If your transfer case requires a fluid with a 6.X cSt viscosity@100C do you really think any fluid with a 12 cSt viscosity@100C would be appropriate?There are at least some 75W-85 gear oils that say both 'transfer cases and differentials'. Shouldn't these hence fulfill the needs of both the diffs front and rear and the transfer case?
RAVENOL MTF-1 SAE 75W-85
RAVENOL MTF-1 SAE 75W-85 is a PAO based full synthetic, low-viscosity transmission oil for special manual transmissions, transfer cases and differential ge...
RAVENOL DGL SAE 75W-85 GL-5 LS
RAVENOL DGL SAE 75W-85 GL-5 LS is full synthetic multi-grade hypoid transmission oil of API GL-5 power class with “limited slip” properties for manual tran...
Some owner manuals also don't have intervals for trans and diff fluids, some also say lifetime fluids. It's a classic bean counter vs engineer issue.