I'm reading MB states the rear diff needs SAE 90..

I found a new bottle of Castrol Hypoy C Gear Oil 80-90...will be ok to use or should I go buy the correct one?
I'm not familiar at all with gear oil.

Thanks,
Robert

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
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2003 Gray Mercedes ML350 - 122k