I like to have the least amount of noise possible in my drivetrains. That way, I can hear if there is an actual problem. Once, there was a deer standing in the middle of the MUP, looking at the couple who had just passed, and I had to yell to get it to move because my freewheel wasn't making any noise.

Heavier weight oil will dampen the sound, but the freewheel may not work as well in cold weather. I just use my garage oil can, which is filled with the remnants of whatever is in the cars, like 10w-30.