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      05-17-2009, 02:21 PM   #36
Brigadier General
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United Kingdom

Drives: 2017 M4 CP DCT
Join Date: Mar 2009
Location: UK

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I had my first discussions with Castrol Tech support in 1997 about Castrol SAF-XJ (for use in the noisy LSD of my 911 turbo) and still have my hand written notes which say he is sending me to try: "4 ltrs of SAF XJ full synthetic APi 75-145 GLs for LSD with Friction Modifiers".
I had another conversation with Castrol when people first had their troubles with noisy E46 diffs and IIRC the same SAF-XJ that I had in 1997 was recommended for the E46 M3s.
I guess it could be that BMW and Castrol made arrangements to produce a custom oil for the M3s diff but I would have expected them not to use the same designation of SAF-XJ which serves only to confuse. But it would be best to be sure, so that everyone has the right info.