We all know that a 0 - 5w multi-grade motor oil flows better in cold weather. We have probably watched videos where this oil is made very cold and poured out and it is very thick.
This made we wonder how thick a 75-90w gear lube must get in cold weather. Is it like frozen ice cream or butter? How the
Consistency of gear lube in very cold weather
- Thread starter ZZman
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Originally Posted By: ZZman
Like ice cream then?.... 
4WD
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Does not get pumped … still requires mobility … some may have noticed the OEM’s went synthetic with gear oil long before getting behind synthetic lubes in the motor …
Like a 10w40 to a 15w50 motor oil. Ive only trashed a diff through shock not through cold running. Though back when I had RRWD diffs with SAE90 I had a garage
I'm sure this has been posted here before, but it's still fun to watch.
Gear Oil in Cold
Originally Posted By: fenixguy
I'm sure this has been posted here before, but it's still fun to watch.
Gear Oil in Cold
4WD
$50 site donor 2023
Yep … 4 speed big blocks got a few …
what's weird is my vehicles i the late 90's came factory filled with either 75w90 or 75w140 synthetic.
and my Parents recently bought a 2015 Ford Escape that is spec'ed for 80w90 in the rear axle......why not 75w90?
I've never seen gear oil in cold weather but I've certainly felt the difference a thinner oil makes.
My BMW motorcycle has gear oil in the gearbox, shaft drive and final drive. Spinning the rear wheel by hand in neutral demonstrates there is a really substantial amount of oil drag at - 5 deg C which is my lower limit for riding. Switching from the specified mineral 80W90 to synthetic 75W90 subjectively reduced that drag by a large amount. When I graphed the oils it was a reduction from approx. 4000 cSt to 1000 cSt. That reduction in cold viscosity has to be worth having and I won't be going back to the 80W90.
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