75w90 auto oil in LU
- Thread starter AS
- Start date
You can and it will be fine ....unless you get some water intrusion from a leaky shaft seal caused by running over some fishing line. Ask me how I know.
The marine lower unit 75W90 will include some emulsifier additives I believe.
The marine lower unit 75W90 will include some emulsifier additives I believe.
You only use 1 to 2 QTs and change it once a year. I would use marine gear oil. Walmart carries a lot. Do cheap out here.
A Volvo Penta lower unit for example is $12K.
A Volvo Penta lower unit for example is $12K.
It will work, but it is not the best. Marine gear oil is different. Here is the BITOG thread:
https://bobistheoilguy.com/forums/threads/marine-gear-oil-vs-regular-gear-oil.278984/
https://bobistheoilguy.com/forums/threads/marine-gear-oil-vs-regular-gear-oil.278984/
I was told years ago that regular car gear oil will get whipped into a froth in the lower unit. Frothy oil isn
t good for lubricating anything that I know of, and being it wasn't a big investment in a qt of marine oil, I went that route and never had an issue with it.,,
t good for lubricating anything that I know of, and being it wasn't a big investment in a qt of marine oil, I went that route and never had an issue with it.,,
But it wouldn't get whipped into a froth in a differential?
Maybe. But there seems to be more room in a differential housing, then a outboards lower unit housing. I also heard that marine oil will perform better, if water gets in in the unit. That might be an old wives tail, but why take a chance ?.,,
I've had water intrusion in my lower unit before, and the marine gear oil just emulsified it like it should. Drains out milky looking. And not more reusing drain/fill plug gaskets for me...
All gear oil will go milky when water is added. Diffs with water in them do the same as a lower unit.
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- Apr 22, 2016
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Personally, I only use automotive gear oil in my LU
When I go to the trouble of draining the gear oil in my VP lower unit I will use VP gear oil. I do it once a year so easy to plan for. If it's not locally available I will order it on Amazon. And changing oil in a VP DuoProp one has to pull both props then open the drain plug that is behind the back prop.
It’s only fine if your seals are in good shape. Questionable seals would mandate marine lube in my mind. I beleive ASTM testing for marine lubes is up to 15% water intrusion by volume and still pass. I doubt an automotive gear lube would handle that.
