# low viscosity transmission oil



## Moltenmetal (Mar 20, 2014)

I use the manual transmission gear oil recommended by the manufacturer, and that's what I'd recommend everyone else do unless they design transmissions for a living. That I'm driving the gearbox with an electric motor rather than an IC engine doesn't change what the gearbox needs for lubrication. In mine, it's thick EP80W90 gear oil, containing the stinky sulphurous "extreme pressure" additives. Yes, it's viscous, and yes it wastes a little energy, but it keeps my 36 yr old gearbox happy especially in the heat of the summer, and that's what matters most to me. 

Regrettably, I don't think any kind of oil I could buy will keep my differential happy- it seems to not like the frequent transitions between hard forward and hard reverse torque (from regen braking) that I challenge it with. I may have to eliminate or reduce my off-pedal regen just to keep it from failing prematurely.


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## Vanquizor (Nov 17, 2009)

If you are looking to get a decrease in fluid drag without loosing protection look to a modern synthetic with a wider viscosity range. 

For example rather than Moltenmetal using a EP80w90 (I'm guessing gl-4 or gl-5) he could use a lube like Menzoil's EP70w90 which would offer the same or slightly higher protection at high temperature/load but would be much thinner when lightly loaded or at lower temperatures.

Similarly if your fill calls for 5w30 you could consider a 0w40 for superior performance both when cold and hot.

Molten- specific to your diff eating, Assuming you have reduced drive line lash to the minimum practical have you tried something like RedLine's Heavy ShockProof as a differential fill?


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## Frank (Dec 6, 2008)

+1 on synthetic. Make sure you get GL-4 or -5 per specifications. I have noticed the difference this makes on motorcycles in cool weather and in a couple of conversions driven during winter months. Less drag = more efficiency.


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