Safe to use 75w-90 in diff. requiring 75w-140???

[jason07-1zzfe]

Based on the analysis just posted of M1 75w90 in a 540i, I think a 140wt may be worth at least a try. At least trying a higher end gear oil like Red Line 75w90. But if the TSB says 140wt, that could be why they saw high wear...

I'd recommend Red Line 80w140 from our site sponsor. Or the 75w140NS and add the FM separately.

 

[VaderSS]

The limited slip in your BMW isn't a Torsen is it?

If it is, then you don't need the FM.

[ June 12, 2003, 03:34 PM: Message edited by: VaderSS ]

 

[7TFord]

If your car does need the limited slip product then you could just add friction modifier to the Castrol 75/90 until the chatter stops. You shouldn't need the protection offered by a 75/140. They use that stuff in trucks and large SUV's.

 

[jason07-1zzfe]

But how do you know he doesn't need that protection? They must spec it in the TSB for a reason. And that 540i with the 75w90 isn't looking pretty.
BMW began a trend somewhere in the 90's of undersizing their diffs, to the point now having to put a clutch delay valve on them to prevent smokey burnout launches from blowing the diff.
I really don't know what's up with that, but it really ticks me off. Part of the reason I prefer my '89 and not really interested in many new ones.

That undersizing probably places addition load on the lube as well...

[ June 12, 2003, 05:09 PM: Message edited by: Jason Troxell ]

 

[Dr. T]

Where is the 540i link?

Once the dealer put in non-LS fluid and I knew something wasn't right (whining sound on sharp turns)...and it did the same thing when I tried the Castro SAF-XO (as per owner's manual). Although I don't know what type of limited slip I have, I know I need limited slip fluid. It's been alright with Mobil 1 synthetic gear lube to date, I just want to know if I really need to install dealer-sourced Castrol SAF-XJ which is a 75w-140 if I really don't need it ie. I'll be fine with M-1. Does M-1 make a 75w-140?

 

[1maniac]

Here's teh link to my 540i's M1 UOA gear lube Mobil 1 Synthetic 75w90 gear oil . BMW uses Castrol SAF-X0 for "Non-LSD only" and BMW's "Synthetic Final Drive Oil" for LSD. The dealer currently recommends their own BMW brand (formulated by Castrol exclusively for BMW) SAF-XLS which has now been superseded by SAF-XJ. However, upon my call to BMW they reccomend only using a fully synthetic 75w90 such as M1 redline or amsoil in the rear end of either LSD or Non-LSD. I did ask about the 75w140 and BMW said it was not neccessary.

 

[Dr. T]

My BMW owner's manual says to use Castrol SAF-XO diff. fluid (75w-90). However this is a non-limited slip fluid...and it must be listed in error because mine has a limited slip and this fluid causes diff. chatter.

I did find a later-dated TSB that states that for BMW's with limited slip to use Castrol SAF-XJ. However this is a 75w-140. Both fluids are synthetic...and very expensive as they are Euro. derived synthetics.

My question is: would it be OK to use an OTC 75w-90 syntetic fluid recommended for limited slip applications and end the confusion or do I really need a 75-w140??? Any other OTC fluids out there that are synthetic and LS applications in a 75w-140??


for standard axles and then goes on to say to use SAF-XJ for

 

[Dr. T]

Good news 1maniac. Thanx for the info. That was the TSB I was referring to. Funny thing is the local dealer that I got the SAF-XO from did not even stock the XJ that was supposed to be used for M3/M5/Z8/Z3's after `01 and the new Z4's. When I asked what they use for these cars, the guy told me "we don't have a lot of M5's coming in for diff. fluid". I thought it was part of the 1-2k maintenance interval. I remember seeing M3's in for this on another occasion at a different dealership. They were putting it Syntec 75w-90 Diff. fluid as they did in my car. Glad to know it's safe to use. Thanx again....

 

[jason07-1zzfe]

I don't think I would trust dealers to use the right fluids...engine or otherwise. Based on the plethora of stories posted here. 5w30 dino in a A3 specd engine? SURE. 15w40 dino in a engine requiring synth! WHYNOT

And you think those dealers saying 90wt is ok have had analysis done on 90 vs 140?

 

[Dr. T]

I agree....except in this case, the screw up was also with the manufacturer...or at least, those who wrote the owner's manual!