Some gear oil designed exclusively for Marine gearcases seems to possess the ability to separate the water from the oil. When the drain plug is removed….water drains first then the oil. I am curious what the designation is for this type of gear oil??
If water is separating out, that is NOT marine gear oil. It is regular 80 or 90 weight gear oil for automotive and other uses. Marine gear oil has an additive that emulsifies water so it combines with it. This helps it keep on lubricating if water gets in. Separation sends water to the bottom off the gearcase and any steel parts in the water (like the gearshift fork in 1950s OMCs) will rust when the motor is upright, not in use, so non-marine gear oil should not be used.
Dave
