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Thread: Lower Unit Oil

  1. #1

    Question Lower Unit Oil

    Do the weights listed by manufacturers take into consideration regional ambient temperatures? In the owners manual, thay list their specified weight, mine's 90 wt. Seems to me, when 90 wt oil sits in 43-48 degree water, it's gonna be pretty thick. Like cold honey. Am i needlessly losing HP because the oil is too thick? Has anyone converted to 75 or 60wt? What are the cons of a lighter oil?
    We never really grow up, we only learn
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  2. #2


    My Volvo 280 outdrive takes the same oil as the motor, 10w-40, as recommended by the manufacturer. I like the idea of 'thicker' vs 'thinner' for more protection, to many variables to really get specific about losing horse power just because of the oil thickness in the lower unit. Maybe if it was a truck up on the slope in the winter that might be an issue.


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