Mower Deck Gear Oil

[RTJ49]

My Kubota ZD 323 calls for 90w gear oil. What is the difference between straight 90w and 75/80w or 80/90w gear oil?
Is any of the other gear oils ok to run?
Thanks,
RTJ49

 

[RjCorazza]

You have the "w" in the wrong place... (which stands for winter).
75w90, 80w90 etc are both 90 weight gear oils. The lower W(inter) will just thicken less in colder temps.
All that said, I have always run 75w140 in all gear cases I have, including the ZD mowers,

 

[KennyG]

In equipment that specifies 90 weight (there are some great internet arguments about whether the "W" stands for weight, winter or winter weight, but they don't matter to us) I always use 75w90 synthetic. I personally don't care for the 75w140. Heavier is not necessarily better, especially for high speed gearing, because it is more likely to not flow well and I like to stay close to the manufacturer specifications. I think it's important to run synthetic since these units go so long between changes.

 

[TractorGuy]

I use whatever I had on the shelf. Changed my finish mower with some 85W90 and my brush mower with some 85W140. I am in FL so the heavy oil won't matter. My Howse mower recommended the 85W140 and my Chinese finish mower recommended the 85W90 so I was good on both counts. I would have used either oil in either mower but since I had them already I stuck with what the manuals said.

 

[Fallon]

All things considered stick with the OEM specifications.

On the other hand any oil or even grease in a consumer tractor gearbox will do fine for a decade or 2 under normal use. Lots of people (including myself) put grease in older gearboxes rather than replace leaky seals letting all the gear oil out. They last for years or decades in that shape.