Is 90w Boat Lower Unit Gear Oil Same as Automotive 90w Gear Oil ?

[al r.]

I have been told it is, Is this true ?

 

[tx1961whaler]

Re: Is 90w Boat Lower Unit Gear Oil Same as Automotive 90w Gear Oil ?

I really don't know, since I'm not the chemist in the factory, but Marine gear oil is supposed to have additives to help in case water gets in the gearcase.

 

[samo_ott]

Re: Is 90w Boat Lower Unit Gear Oil Same as Automotive 90w Gear Oil ?

Yes, they're the same weight and as mentioned the outboard one has additives so that if there's water in your LU, it'll work better than with normal oil.

 

[5150abf]

Re: Is 90w Boat Lower Unit Gear Oil Same as Automotive 90w Gear Oil ?

You were told wrong, rear ends in cars aren't designed to run under water, lower units were.

As stated, lower unit oil has additives to deal with water intrusion, gear oil doesn't.

If you are in a pinch I have gone out for one trip with gear oil but I changed it again before the next trip, note to self, check to see if you have oil before draining lower.

I check mine every other trip by cracking the bottom drain screw on the lower and checking for water and change it at least once a year, oil is ALOT cheaper than a new lower.

 

[ryendube]

Re: Is 90w Boat Lower Unit Gear Oil Same as Automotive 90w Gear Oil ?

water resistance and anti foam. Normal auto/truck gear oils will entrain water and turn grey and foam.
The foamy grey mass takes up more space that the gear oil itself, resulting in overflow at all ventable or weak seal points.A specific marine synthetic will be designed to work in a wet environment.
Water will also strip out required additives in gear and motor oils that are not designed to work with water, resulting in lubrication failure.

 

[wilde1j]

Re: Is 90w Boat Lower Unit Gear Oil Same as Automotive 90w Gear Oil ?

I really don't know, since I'm not the chemist in the factory, but Marine gear oil is supposed to have additives to help in case water gets in the gearcase.

This is true. Marine gear oils have emulsifiers and other additives that allow them to cope with some water. Auto gear oils don't, since there's no need. The marine gear oils also have anti-foaming additives, which are important to provide lubrication when getting really churned up by fast rotating gears.