Differential Oil Selection Confusion

[martinq]

Thanks for the ideas. OE fluid from Bmw dealer is very expensive. As I stated earlier I can only get Febi 75w80 hypoid G1 GL5 and Febi 75w85 Hypoid G3 GL5.

Both has bmw recommendations. 70w80 is for my G20 as I see but it says until 2 / 20 and my car was produced at 7/ 20 which is a little bit confusion too.

75w85 is for f30 which was my previous Bmw.

Trying 75w85 is less risky i think as it is in the middle range between 70w80 and 75w90... .

There is no risk in using 75w90. You are not in a "cold climate".

If you can't get 75w90 for a reasonable price then I would use 75w85 but I would not use 75w85 to save money.

Again, viscosity is not that important until you hit the extremes (temperature / racing). 75w85 should be slightly more efficient than 75w90 at the potential cost of wear. Wear contaminates the fluid and leads to more wear if not changed out in time. You won't really know unless you use continuous testing to monitor your application.

 

[moonlightblue]

There is no risk in using 75w90. You are not in a "cold climate".

If you can't get 75w90 for a reasonable price then I would use 75w85 but I would not use 75w85 to save money.

Again, viscosity is not that important until you hit the extremes (temperature / racing). 75w85 should be slightly more efficient than 75w90 at the potential cost of wear. Wear contaminates the fluid and leads to more wear if not changed out in time. You won't really know unless you use continuous testing to monitor your application.

Thanks but I wrote wrong Bmw G3 is 70w80 not 75w85. Annoying thing is to change the first cold temp. weight from 70 to 75 is it still okay? Will 70w80 which is the recommended oil, wear it out much quicker ?

BMW does not recommend 70w80 for no reason, but on the other hand I know how hungry are car manufacturers to make profits from new car sales, and destroying your car with wrong fluids is the only way to do that. So I am not sure which one BMW chose at G20 series. Definitely BMW is the last one to ask, they never reply any email anyway.

 

[martinq]

Thanks but I wrote wrong Bmw G3 is 70w80 not 75w85. Annoying thing is to change the first cold temp. weight from 70 to 75 is it still okay? Will 70w80 which is the recommended oil, wear it out much quicker ?

BMW does not recommend 70w80 for no reason, but on the other hand I know how hungry are car manufacturers to make profits from new car sales, and destroying your car with wrong fluids is the only way to do that. So I am not sure which one BMW chose at G20 series. Definitely BMW is the last one to ask, they never reply any email anyway.

I will quote myself,
"viscosity is not that important until you hit the extremes (temperature / racing)"
"75w85 should be slightly more efficient than 75w90 at the potential cost of wear"

 

[moonlightblue]

I will quote myself,
"viscosity is not that important until you hit the extremes (temperature / racing)"
"75w85 should be slightly more efficient than 75w90 at the potential cost of wear"

Okay thank you very much Martinq

 

[moonlightblue]

Lastly as I research the BMW part number 83222413512 on google I see that even genuine BMW fluid is for non limited slip differentials but I find this info from part sellers websites which can be wrong. So is my differential limited slip or non limited slip? Does anyone have any idea? Febi also does not have technical data sheet for this product 184247 and I did not see any info about being limited slip compatible or not. At Ravenol website the differential fluid of Ravenol 1221112 is limited slip which is even written on its bottle.

 

[goblin]

Lastly as I research the BMW part number 83222413512 on google I see that even genuine BMW fluid is for non limited slip differentials but I find this info from part sellers websites which can be wrong. So is my differential limited slip or non limited slip? Does anyone have any idea? Febi also does not have technical data sheet for this product 184247 and I did not see any info about being limited slip compatible or not. At Ravenol website the differential fluid of Ravenol 1221112 is limited slip which is even written on its bottle.

Find the m539Restorations channel on YouTube, from there see what exactly was the name of his second channel (possibly m539Plus), from there find one of the only three videos currently there, about his 850's differential rebuild, see what was the company that did the rebuild, drop them an email. Sounds long but it won't be.

Unless you fall down the rabbit hole of watching all videos, which you'll probably do.