In Reply to: Re: The Hydraulic Oil Story posted by 36 coupe on December 28, 2013 at 21:31:17:
After attending the TOH school of oil last year and being a graduate of "Bob is the oil guy online university" would have to side with 36 coupe in this debate.
After plotting the viscosity specs of (1)UTF M2C 134-D, (2)80W-90 gear oil ,(3) 90 gear oil & (4)AW46 hydraulic oil, @40C & 100C on the Widman calculator, it obvious that 90 wt gear oil is much more thicker(viscous) than UTF at 100F( summer months ambient temperature).
kinematic viscosity at 100F
SAE 90 gear oil: 250 cSt
SAE 80W-90 gear oil: 165 cSt
UTF M2C 134-D: 62 cSt
AW46 hydraulic oil: 53 cSt
Note: viscosity of SAE 90 gear oil at 100F is 4X the viscosity of UTF.
So, with a highly worn hydraulic pump using SAE 90 oil, would produce greater pressurethan using UTF, resulting in greater lifting capacity.
However, the SAE 90 maybe a bit sluggish at 32F for plowing snow.
80W-90, having 2.5X the viscosity of UTF at 100F, might work better for both summer and winter months. Do not believe single viscosity SAE 80 is still available.
Note that the viscosity of the UTF and AW 46 hydraulic fluid is nearly of equal viscosity at 100F. The UTF behaves like hydraulic oil at 100F temperature.
source of viscosity data
SAE 90 gear oil: Chevron rpm gear oil
80W-90, UTF M2C 134-D & AW 46 : Warren Distributing/Traveller brand/TSC retail store
On the 9n/8N with common sump for differential, hydraulic pump & transmission,
prefer the SAE 90 GL-1. Chevron rpm contains a metal deactivator to stop such metals as copper as found in the scotch yoke hydraulic pump from acting as catalyst to promote oil oxidation. However the SAE 90 from Mercury Marine contains additives to counter act water, which easily enters the common sump through the hydraulic controls causing sludge.
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