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sae 90

  1. SAE 90 vs 75W-90 Is this OK????????

    General 6.0L Discussion
    I am going to change the fluids in my front/rear differential and transfer case. I have looked in my manual for the proper viscosities and quantities. Question: My manual says to use SAE 90 in the front differential but I see folks seem to be using 75W-90. Is this acceptable and why? I have...