Wethead Final Drive Lubricant Specification

stooie · Aug 6, 2020

Can anyone point me to where BMW specifies what fluid is to be used in the final drive on a 2018 RT? My first self-conducted final drive lube change is coming up and I want to be unassailable should a warrantee issue come up somewhere down the road.

I've searched the owners manual but darned if I can find any guidance there.

Note: What I'm searching for is what BMW specifies and the document trail to that specification; not what folks have used and been satisfied with.

Thanks!

r0ckrat · Aug 6, 2020

Based on this service kit, I'd wager 75w90 GL-5 rated gear oil...

https://www.beemerboneyard.com/r1200wcsmaintkit.html

My Haynes is in the garage, I can check it later.

stooie · Aug 6, 2020

Thanks, rOckrat.

I expect you're right that it's 75W-90 GL-5.

I'll save you a trip to the garage; Haynes says it's Castrol SAF-XO of an unspecified viscosity and API rating. I should have mentioned that in my original post. I'd like to go one step deeper and find a BMW reference to the requirement.

Alas, I've been unable to find SAF-XO available on-line.

Ride long and prosper!

cap · Aug 6, 2020

I use Lucas synthetic... exceeds GL-5. Cheap. Works great.

danm · Aug 6, 2020

i don't believe the final drive has changed since the wethead was introduced. My 2020 RT calls for 70W80. BMW sells it as "G3" - about $50 for a 500ml bottle was the cheapest I found. I bought one and did the first change and will use it for the second but will go back to using 75W90 full synthetic as I have for the past 9 years in my 2011 GS.

r0ckrat · Aug 6, 2020

danm said:
i don't believe the final drive has changed since the wethead was introduced.

Other than switching sides, has it really changed from previous iterations?

Dann · Aug 6, 2020

Alas, I've been unable to find SAF-XO available on-line.

On my 07RT, I've been using : 2003-2009 Land Rover Range Rover Differential Oil - Rear Differential - Castrol LRN7591 - Syntrax Long Life; Equivalent to: Castrol SAF-XO)
It's available from Land Rover dealers and half the price of the SAF-XO
It's the same thing rebranded.

My R1250RT manual calls for SAE 70W80 hypoid axle G3

I haven't seen this anywhere. Not on the shelves at the dealer. I've only seen BMW 75/90
Next time I'm at the dealer I'll ask what they put in for the service.

The bill from my 600mi service doesn't mention it.

rangerreece · Aug 6, 2020

180ml

Is this official enough? Just changed mine out last Saturday. I change mine out every 6000 miles with the engine oil change, seems like a good idea to keep that rear drive healthy.

52184 · Aug 6, 2020

Castrol has renamed or replaced SAF-XO. It is now called Castrol Syntrax Long Life 75w-90

Best,
DeVern

rangerreece · Aug 6, 2020

GTRider said:
Castrol has renamed or replaced SAF-XO. It is now called Castrol Syntrax Long Life 75w-90

Best,
DeVern

Thanks for the update, seems like they’re always rebranding the stuff.

Rainman48 · Aug 7, 2020

Under the June 2020 update of the official (and regularly updated) BMW DVD Repair Manual (K5x, K50, K51, K52) under the R 1200 RT (0A13) (USA) category has this to say:

Gear oil (Hypoid Axle Oil G3)

Plain and simple. No brand names, no recommended stores or dealerships. No preferences given. Nothing else. Just what you asked for.

rangerreece · Aug 7, 2020

Rainman48 said:
Under the June 2020 update of the official (and regularly updated) BMW DVD Repair Manual (K5x, K50, K51, K52) under the R 1200 RT (0A13) (USA) category has this to say:

Gear oil (Hypoid Axle Oil G3)

Plain and simple. No brand names, no recommended stores or dealerships. No preferences given. Nothing else. Just what you asked for.

If only my computer had a dvd reader, and was a PC. last repair manual I had, wasn’t compatible. Thanks for sharing here.

stooie · Aug 7, 2020

Rainman48 said:
Under the June 2020 update of the official (and regularly updated) BMW DVD Repair Manual (K5x, K50, K51, K52) under the R 1200 RT (0A13) (USA) category has this to say:

Gear oil (Hypoid Axle Oil G3)

Plain and simple. No brand names, no recommended stores or dealerships. No preferences given. Nothing else. Just what you asked for.

Rainman48:

THANK YOU! THANK YOU! THANK YOU!

Does the update mention viscosity?

pglaves · Aug 7, 2020

Rainman48 said:
Under the June 2020 update of the official (and regularly updated) BMW DVD Repair Manual (K5x, K50, K51, K52) under the R 1200 RT (0A13) (USA) category has this to say:

Gear oil (Hypoid Axle Oil G3)

Plain and simple. No brand names, no recommended stores or dealerships. No preferences given. Nothing else. Just what you asked for.

I wonder who sued whom?

Rainman48 · Aug 7, 2020

stooie said:
Rainman48:

THANK YOU! THANK YOU! THANK YOU!

Does the update mention viscosity?

Nope,... just those 6 words.
Since you didn't want preferences, that's what I gave you, and now you want more. Tisk, tisk.

Maybe you already have, but I suggest you look up the G3 or GL-3 specifications for more details, or copy and Google those 6 words. You might be surprised at what shows up. "Hypoid gear" is essential as that is how our FD's are cut and from what I see it's what is needed for the added pressure components. I'd assume GL-3 is a minimum for hypoid gears that meets BMW's approval. For viscosity, I'd look at BMW's "current" brand (they change frequently to hide their supplier) to see what they are using, then pick one.

danm · Aug 7, 2020

You should know that GL-3 and BMW's G3 are two different things. "GL" is an API rating. GL-3 is pretty much an obsolete gear oil. Most everything on the road calls for GL-4 or GL-5.

"G3" is a BMW name for their current gear oil. They've offered G1, G2, G3, G4 & G5. From what I've been able to find all the current BMW Hypoid oils carry an API rating of GL-4 or GL-5. GL-4 is usually for transmissions and GL-5 is for differentials. They have different additive packages. Some have additives for limited slip differentials in cars but it's not an issue in vehicles without limited slip. (or motorcycles)

The only question is viscosity. BMW's G3 (and what the manual on my '20 RT calls for) is 70W80. The trend of going to thinner lubricants is for fuel economy. If they spec'd thinner lubricant in their automotive line, it would follow that they are condensing part numbers and just using their "G3 70W80" across the board in current vehicles.

I can't see any reason a base viscosity of 75 in GL-5 vs 70 in BMW's G3 would have any adverse effect. It is only going to matter when extremely cold and the difference is negligible.

pglaves · Aug 7, 2020

danm said:
I can't see any reason a base viscosity of 75 in GL-5 vs 70 in BMW's G3 would have any adverse effect. It is only going to matter when extremely cold and the difference is negligible.

I would be curious as to what bearings they are now using, and whether they are sealed with grease or lubricated by the gear oil. I know that in the Oilhead generation the bearings were gear oil lubricated and were specified as a C5 extra-clearance bearing to ensure that the gear oil could adequately flow in between the balls and races, and that using high viscosity gear oil xxW140 gear oil contributed to final drive failures.

craigjv4 · Aug 7, 2020

G3 for 50 bucks a bottle or the bottle Reece showed which is what I have for 12 bucks.

I also changed my final drive oil at every oil change and since she was new, I used a 4000 miles interval. Now that shes "broken-in", I'm following the 6000 miles interval for engine and final drive oil.

stooie · Aug 7, 2020

danm said:
You should know that GL-3 and BMW's G3 are two different things. "GL" is an API rating. GL-3 is pretty much an obsolete gear oil. Most everything on the road calls for GL-4 or GL-5.

"G3" is a BMW name for their current gear oil. They've offered G1, G2, G3, G4 & G5. From what I've been able to find all the current BMW Hypoid oils carry an API rating of GL-4 or GL-5. GL-4 is usually for transmissions and GL-5 is for differentials. They have different additive packages. Some have additives for limited slip differentials in cars but it's not an issue in vehicles without limited slip. (or motorcycles)

DanM: Yup; I sussed that out. BMW doesn't do us any favors by not being a little more open in lube specifications. As I understand it, there is a big difference in the additive packages in GL-4 and GL-5. One has hypoid extreme pressure additives (chlorine or sulfur based) which can corrode/erode bronze/copper parts in some auto limited slip diffs and transmissions. The G3 specification really doesn't tell us much.

In general, OEMs will specify a generic lube spec, i.e., API SL, GL-4, or whatever. When they miss on their design and need a really special lube to cover up for their design deficiency, they go to some obscure or proprietary spec. (Ask me how I know; I worked for a helicopter OEM.)

Ain't life interesting?

stooie · Aug 8, 2020

Status Report

Thanks to all who responded! Here's what I've found so far:

1. The owner’s manual for my 2018 RT makes no reference to a specified final drive fluid.

2. The June 2020 update to the BMW DVD Service Manual specifies the following for the R1200RT:

Gear oil (Hypoid Axle Oil G3)

There is no mention I can find of a viscosity or API rating for G3 oil.

GetBMWParts.com (a BMW auto parts site) has G3 for $46.10 for a 500-ml jug.

3. My Haynes manual, published in 2016, specifies Castrol SAF-XO.

Bimmerworld.com (another BMW auto parts site) has BMW branded C-SAF-XO labeled as Synthetic, 70W-90, GL-5. It’s $20.16 for a 1-liter jug.

I leave it to you to draw your own conclusions about the reason for the change from SAF-XO to G3. Technical issue? Commonality with their automobile specs? Profit margin?

Enjoy the ride!

Wethead Final Drive Lubricant Specification

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