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      01-13-2011, 04:42 AM   #21
SenorFunkyPants
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Note that Castrol don't make the SAF-XJ with extra friction modifiers, its a third party formulation and that Castrol generally don't recommend extra oil changes for the SAF XJ diff oil over and above the scheduled changes.
Also the typical diff groan is more likely to appear in a lightly used car especially one that does most of its miles on the highway.