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Message Subject: Lower unit Gear Lube: sae 90 vs 80W-90

tolle141

Posted 11/6/2017 11:33 AM (#883521)
Subject: Lower unit Gear Lube: sae 90 vs 80W-90

Posts: 1000

Hey Everyone,

Planning on winterizing the motor Wednesday afternoon. My motor (honda 135) requires SAE 90. What's the difference between SAE 90 and 80W-90? Seem to find a lot more of that around.

Thanks!

esoxaddict

Posted 11/6/2017 4:56 PM (#883584 - in reply to #883521)
Subject: Re: Lower unit Gear Lube: sae 90 vs 80W-90

Posts: 8781

Straight-weight oils maintain their viscosity throughout the range of operating temperatures. Multi-viscosity oils (i.e.10w30 for example) is basically a 10 weight oil with additives that cause it to perform like a 30 weight oil at higher temperatures.

Great for internal combustion engines that are required to start and run in cold temperatures.

For a lower unit? Not sure it matters as much, if at all...

Edited by esoxaddict 11/6/2017 5:25 PM

VMS

Posted 11/7/2017 12:51 PM (#883646 - in reply to #883521)
Subject: Re: Lower unit Gear Lube: sae 90 vs 80W-90

Posts: 3480

Location: Elk River, Minnesota

Hiya,

If memory serves me correctly, the 80W-90 is just a multi-weight viscosity oil. The two numbers have to do with temperature of some sort. Please don't quote me directly on this but I believe it is something like it acts like 80 weight oil at cold temp and 90 weight oil at high temp in terms of viscosity, or it's ability to flow.

Regardless, so long as the marine gear oil fits under your specifications for the outboard, you should be just fine. I happen to run amsoil synthetic marine gear oil, which I believe would also fit your application. This runs at 75W-90 so it should suffice for the needs of 90 weight oil and any extreme pressure situation as well.

https://www.amsoil.com/shop/by-product/gear-lube/universal-synthetic...

Steve

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