Quote:
Originally Posted by Aronis
This part number differs from that BMW part number listed on the above service record posted by a customer who had his 1200 mile service done.
I found it listed on ECS but no specs on the weight. I found that weight information I listed above elsewhere. Where did you find your info on the Castrol product?
Mike
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This is what I know based on what I was told by techs.
The difference between the two types of rear diff oil is the addition of more friction modifiers (FM) than normal diff oil. The oil put in mine does not have the additional friction modifier but it is also synthetic 75w140, just like the FM version. According to two techs I spoke with, the addition of more friction modifier was a US only requirement for older M cars (E46, E92, F80) since the diff would make groaning noises during low speed cornering, which in normal and does not mean anything is wrong. US customers apparently complained of the groan and BMW added friction modifiers, which actually slightly reduce the performance of the diff. The diff in the F10 M5 did not have this issue and you were able to use SAF-XJ without any noise from the diff. You should be fine with either one. If you get 83-22-2-357-992 (SAF-XJ) and you hear groaning noises during low speed cornering, then you may want the one with the Friction Modifier (SAF-XJ-FM part 83 22 2 447 362). With that said, diff chatter is bad, groaning is perfectly fine.
No noise from my car after 100 miles since the change.
SAF-XJ is a synthetic, very high quality diff oil that's actually used in the E63s rear diff.
Based on all the research on differentials I have done these past few days, I'm sticking with the SAF-XJ.
Check out this thread on why people prefer no friction modifier in their diff:
http://www.m3post.com/forums/showthread.php?t=1317480