Several years ago Machinery Lubrication did a story about synthetic gear oil They stated in the article spiral and hypoid gears reaped the most benefit from synthetic oil. More so than engine oil. Less mechanical loss and cooler operation. If I wasn't so lazy I would look it up.
Synthetic vs Conventional Diff. Lube
- Thread starter grachik
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I couldn't find the article I was referring to but here are a few (of many) good reads from Machinery Lubrication:
https://www.machinerylubrication.com/Read/29954/synthetic-gear-oil
https://www.machinerylubrication.com/Read/167/synthetic-gear-oil
https://www.machinerylubrication.com/Read/29954/synthetic-gear-oil
https://www.machinerylubrication.com/Read/167/synthetic-gear-oil
If a final drive or gearbox becomes more efficient when using synthetic oil,then logically the oil temperature will be lower and viscosity higher for the synthetic compared to the equivalent mineral oil in any given set of conditions. This begs the question of whether a lower viscosity synthetic should have being chosen in the first place. For example a 75W85 instead of an 75W90.
Originally Posted by ka9mnx
I couldn't find the article I was referring to but here are a few (of many) good reads from Machinery Lubrication:
https://www.machinerylubrication.com/Read/29954/synthetic-gear-oil
https://www.machinerylubrication.com/Read/167/synthetic-gear-oil
Thank you. According to the articles, even a lowly mineral oil should be good for 200k miles in old geezer mode.
==============================
Synthetic oils have better resistance to aging and high temperatures and a longer service life than mineral oils. Depending on the base oil (SHC or PAG), the oil change intervals may be three to five times longer at the same operating temperature.
Approximate oil change intervals of gear oils at an operating temperature of 176°F (80°C) are:
Mineral oil: 5,000 operating hours
SHC oil: 15,000 operating hours (extension factor 3)
PAG oil: 25,000 operating hours (extension factor 5)
Synthetic oils have a lower friction coefficient than mineral oils in a gearbox and a more favorable viscosity-temperature relationship. This generally permits the use of synthetics at lower viscosity grades and also offers the possibility of reduced oil temperature during operation. In such cases, the life extension factors for oil change intervals of synthetic oils are longer than the values stated above, which refer to identical oil temperature.
The following comparison of test results illustrates this advantage. Three lubricants were tested in a splash lubricated worm gear test rig.
The test records show the following oil sump temperatures after 300 operating hours:
Mineral oil: 230°F (110°C)
SHC: 194°F (90°C)
PAG: 167°F (75°C)
The life extension factors of synthetic oils as compared to mineral oil are as follows:
Mineral oil = 1
SHC = 9.5 times longer
PAG = 31 times longer
I couldn't find the article I was referring to but here are a few (of many) good reads from Machinery Lubrication:
https://www.machinerylubrication.com/Read/29954/synthetic-gear-oil
https://www.machinerylubrication.com/Read/167/synthetic-gear-oil
Thank you. According to the articles, even a lowly mineral oil should be good for 200k miles in old geezer mode.
==============================
Synthetic oils have better resistance to aging and high temperatures and a longer service life than mineral oils. Depending on the base oil (SHC or PAG), the oil change intervals may be three to five times longer at the same operating temperature.
Approximate oil change intervals of gear oils at an operating temperature of 176°F (80°C) are:
Mineral oil: 5,000 operating hours
SHC oil: 15,000 operating hours (extension factor 3)
PAG oil: 25,000 operating hours (extension factor 5)
Synthetic oils have a lower friction coefficient than mineral oils in a gearbox and a more favorable viscosity-temperature relationship. This generally permits the use of synthetics at lower viscosity grades and also offers the possibility of reduced oil temperature during operation. In such cases, the life extension factors for oil change intervals of synthetic oils are longer than the values stated above, which refer to identical oil temperature.
The following comparison of test results illustrates this advantage. Three lubricants were tested in a splash lubricated worm gear test rig.
The test records show the following oil sump temperatures after 300 operating hours:
Mineral oil: 230°F (110°C)
SHC: 194°F (90°C)
PAG: 167°F (75°C)
The life extension factors of synthetic oils as compared to mineral oil are as follows:
Mineral oil = 1
SHC = 9.5 times longer
PAG = 31 times longer
Originally Posted by Y_K
Originally Posted by ka9mnx
I couldn't find the article I was referring to but here are a few (of many) good reads from Machinery Lubrication:
https://www.machinerylubrication.com/Read/29954/synthetic-gear-oil
https://www.machinerylubrication.com/Read/167/synthetic-gear-oil
Thank you. According to the articles, even a lowly mineral oil should be good for 200k miles in old geezer mode.
==============================
Synthetic oils have better resistance to aging and high temperatures and a longer service life than mineral oils. Depending on the base oil (SHC or PAG), the oil change intervals may be three to five times longer at the same operating temperature.
Approximate oil change intervals of gear oils at an operating temperature of 176°F (80°C) are:
Mineral oil: 5,000 operating hours
SHC oil: 15,000 operating hours (extension factor 3)
PAG oil: 25,000 operating hours (extension factor 5)
Synthetic oils have a lower friction coefficient than mineral oils in a gearbox and a more favorable viscosity-temperature relationship. This generally permits the use of synthetics at lower viscosity grades and also offers the possibility of reduced oil temperature during operation. In such cases, the life extension factors for oil change intervals of synthetic oils are longer than the values stated above, which refer to identical oil temperature.
The following comparison of test results illustrates this advantage. Three lubricants were tested in a splash lubricated worm gear test rig.
The test records show the following oil sump temperatures after 300 operating hours:
Mineral oil: 230°F (110°C)
SHC: 194°F (90°C)
PAG: 167°F (75°C)
The life extension factors of synthetic oils as compared to mineral oil are as follows:
Mineral oil = 1
SHC = 9.5 times longer
PAG = 31 times longer
Does it occur to us that :
Operating viscoisities of PAG >> is higher than that of SHC, >>>> which in turn is higher than that of Mineral oil, hence leading to
Operating temperatures PAG whilst all these 3 oils are of similar viscosity grades at KV@40*C in the context of industrial gear oils , which the article fails to highlight or not expressed.
It's the operating viscosities that matters, not (base) oil groups per se.
It's confusing, I know.
Edit:Mineral gear oil operating at 110*C is simply an incorrect viscosity grade selection by owner , other than gearbox design dificiency.
Originally Posted by ka9mnx
I couldn't find the article I was referring to but here are a few (of many) good reads from Machinery Lubrication:
https://www.machinerylubrication.com/Read/29954/synthetic-gear-oil
https://www.machinerylubrication.com/Read/167/synthetic-gear-oil
Thank you. According to the articles, even a lowly mineral oil should be good for 200k miles in old geezer mode.
==============================
Synthetic oils have better resistance to aging and high temperatures and a longer service life than mineral oils. Depending on the base oil (SHC or PAG), the oil change intervals may be three to five times longer at the same operating temperature.
Approximate oil change intervals of gear oils at an operating temperature of 176°F (80°C) are:
Mineral oil: 5,000 operating hours
SHC oil: 15,000 operating hours (extension factor 3)
PAG oil: 25,000 operating hours (extension factor 5)
Synthetic oils have a lower friction coefficient than mineral oils in a gearbox and a more favorable viscosity-temperature relationship. This generally permits the use of synthetics at lower viscosity grades and also offers the possibility of reduced oil temperature during operation. In such cases, the life extension factors for oil change intervals of synthetic oils are longer than the values stated above, which refer to identical oil temperature.
The following comparison of test results illustrates this advantage. Three lubricants were tested in a splash lubricated worm gear test rig.
The test records show the following oil sump temperatures after 300 operating hours:
Mineral oil: 230°F (110°C)
SHC: 194°F (90°C)
PAG: 167°F (75°C)
The life extension factors of synthetic oils as compared to mineral oil are as follows:
Mineral oil = 1
SHC = 9.5 times longer
PAG = 31 times longer
Does it occur to us that :
Operating viscoisities of PAG >> is higher than that of SHC, >>>> which in turn is higher than that of Mineral oil, hence leading to
Operating temperatures PAG whilst all these 3 oils are of similar viscosity grades at KV@40*C in the context of industrial gear oils , which the article fails to highlight or not expressed.
It's the operating viscosities that matters, not (base) oil groups per se.
It's confusing, I know.
Edit:Mineral gear oil operating at 110*C is simply an incorrect viscosity grade selection by owner , other than gearbox design dificiency.
Last edited:
Originally Posted by barryh
If a final drive or gearbox becomes more efficient when using synthetic oil,then logically the oil temperature will be lower and viscosity higher for the synthetic compared to the equivalent mineral oil in any given set of conditions.
If a final drive or gearbox becomes more efficient when using synthetic oil,then logically the oil temperature will be lower and viscosity higher for the synthetic compared to the equivalent mineral oil in any given set of conditions.
4WD
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Originally Posted by BJD78
Exactly that' s the Truth right there. Most Owner manual maintenence schedules recommend changing somewhere between 30K and 60K.
Most do eh ?
Exactly that' s the Truth right there. Most Owner manual maintenence schedules recommend changing somewhere between 30K and 60K.
Most do eh ?
4WD
$50 site donor 2024
What is in the owners manual ? - IIRC, synthetic gear oil was recommended before synthetic motor oil was.
Originally Posted by Y_K
Thank you, zeng and barryh for the clarity.
The writer couldn't differentiate the Dynamic Coefficient of Friction and its dominant heat generation (arising from boundary lubrication regimes) fromTraction Coefficient of Friction and its marginal heat generation (arising from fluid drag) ,hence the confusing positions .
Thank you, zeng and barryh for the clarity.
The writer couldn't differentiate the Dynamic Coefficient of Friction and its dominant heat generation (arising from boundary lubrication regimes) fromTraction Coefficient of Friction and its marginal heat generation (arising from fluid drag) ,hence the confusing positions .
Last edited:
Originally Posted by Jimzz
Not a lot difference. But the price difference is pretty small if you shop around. Walmarts Supertech 75w90 and 75w140 is pretty cheap and good quality. So I run the syn in all the diffs I work on.
Any idea if Super Tech makes a synthetic 80W-90? I couldn't find one. Any idea what the Super Tech data sheets look like? I'd love to compare kinematic viscosity of the synthetic 75W-90 to to the conventional 80W-90.
Not a lot difference. But the price difference is pretty small if you shop around. Walmarts Supertech 75w90 and 75w140 is pretty cheap and good quality. So I run the syn in all the diffs I work on.
Any idea if Super Tech makes a synthetic 80W-90? I couldn't find one. Any idea what the Super Tech data sheets look like? I'd love to compare kinematic viscosity of the synthetic 75W-90 to to the conventional 80W-90.
I don't think ST makes a syn 80w-90. Why would you want/need that grade?
Here are the specs from my notes for ST:
SupertTech Syn
75w90
100C 16.15
40C 109.3
VI 159
75w-140
40C 27.64
100C 171.8
VI 200
SuperTech Conv
75w-90
100C 13.98
40C 130.9
VI 104
75w-140
100C 26.39
40C 347.7
VI 100
Here are the specs from my notes for ST:
SupertTech Syn
75w90
100C 16.15
40C 109.3
VI 159
75w-140
40C 27.64
100C 171.8
VI 200
SuperTech Conv
75w-90
100C 13.98
40C 130.9
VI 104
75w-140
100C 26.39
40C 347.7
VI 100
Originally Posted by ka9mnx
I don't think ST makes a syn 80w-90. Why would you want/need that grade?
Here are the specs from my notes for ST:
SupertTech Syn
75w90
100C 16.15
40C 109.3
VI 159
75w-140
40C 27.64
100C 171.8
VI 200
SuperTech Conv
75w-90
100C 13.98
40C 130.9
VI 104
75w-140
100C 26.39
40C 347.7
VI 100
Thanks! I just saw that, actually. I think I'm not fully understanding how to best choose my oil, based on the viscosity. I have "80W-90" in my head, since the manufacturer recommends it on my 2000-2004 Nissan Xterras and Frontiers (actually OEM oil was 75W-85), but I realize the kinematic viscosity at 40C and 100C on the ST 75W-90 are still within the range of all the 80W-90's I've been researching.
What is the rule of thumb (or is it not that simple) when choosing a gear oil? I'm also trying to see if I can match the oil choice with some other vehicles my friends have, in order to try and keep overall costs down (buying by the 5 gallon bucket).
I've also run into murky waters, dealing with LSD additives. All the vehicles have LSD, some with break-away-torque figures that vary wildly, so I'm trying to find answers to concentration levels of LSD additives in each product. I was hoping to either use an oil with NO modifier in it and add my own, or find a conventional oil that has *some* additive in it (marketed as appropriate for LSD differentials) and try that on the majority of the vehicles, and add more additive if there is still chatter on some of the more aggressive LSD's in some vehicles.
I became super confused when Valvoline told me they add 4 oz of additive to each quart of 80W-90 synthetic gear oil, when the average bottle of additive sold separately suggests 4 oz per 2-quart axle (add more if larger than 2 quart axles). I was also told my the Napa guys that most of their customers complained they still had chatter when using the full synthetic gear oil (supposedly with 4 oz modifier in each quart) so they are all adding more, even to the synthetic. Having said that, Napa guys didn't know the conventional oil "used" to have LSD additives in it, until a year ago, and then Valvoline just removed the additives and didn't tell anyone - and continued using the same part number and removed the "Limited Slip" from the bottle. Ugh!
I wonder if WPP would comment on the amount of LSD additives (oz per quart) in their ST synthetic 75W-90? That might help me understand where to go from here. That viscosity looks like it should work in my applications. I don't have any idea what the kinematic viscosity was in the OEM 75W-85 from Nissan.
I don't think ST makes a syn 80w-90. Why would you want/need that grade?
Here are the specs from my notes for ST:
SupertTech Syn
75w90
100C 16.15
40C 109.3
VI 159
75w-140
40C 27.64
100C 171.8
VI 200
SuperTech Conv
75w-90
100C 13.98
40C 130.9
VI 104
75w-140
100C 26.39
40C 347.7
VI 100
Thanks! I just saw that, actually. I think I'm not fully understanding how to best choose my oil, based on the viscosity. I have "80W-90" in my head, since the manufacturer recommends it on my 2000-2004 Nissan Xterras and Frontiers (actually OEM oil was 75W-85), but I realize the kinematic viscosity at 40C and 100C on the ST 75W-90 are still within the range of all the 80W-90's I've been researching.
What is the rule of thumb (or is it not that simple) when choosing a gear oil? I'm also trying to see if I can match the oil choice with some other vehicles my friends have, in order to try and keep overall costs down (buying by the 5 gallon bucket).
I've also run into murky waters, dealing with LSD additives. All the vehicles have LSD, some with break-away-torque figures that vary wildly, so I'm trying to find answers to concentration levels of LSD additives in each product. I was hoping to either use an oil with NO modifier in it and add my own, or find a conventional oil that has *some* additive in it (marketed as appropriate for LSD differentials) and try that on the majority of the vehicles, and add more additive if there is still chatter on some of the more aggressive LSD's in some vehicles.
I became super confused when Valvoline told me they add 4 oz of additive to each quart of 80W-90 synthetic gear oil, when the average bottle of additive sold separately suggests 4 oz per 2-quart axle (add more if larger than 2 quart axles). I was also told my the Napa guys that most of their customers complained they still had chatter when using the full synthetic gear oil (supposedly with 4 oz modifier in each quart) so they are all adding more, even to the synthetic. Having said that, Napa guys didn't know the conventional oil "used" to have LSD additives in it, until a year ago, and then Valvoline just removed the additives and didn't tell anyone - and continued using the same part number and removed the "Limited Slip" from the bottle. Ugh!
I wonder if WPP would comment on the amount of LSD additives (oz per quart) in their ST synthetic 75W-90? That might help me understand where to go from here. That viscosity looks like it should work in my applications. I don't have any idea what the kinematic viscosity was in the OEM 75W-85 from Nissan.
Originally Posted by Spddm0n
What is the rule of thumb (or is it not that simple) when choosing a gear oil? I'm also trying to see if I can match the oil choice with some other vehicles my friends have, in order to try and keep overall costs down (buying by the 5 gallon bucket).
My rule of thumb would be match the GL rating the manufacturer specifies (GL-4, GL-5, etc.).
Match the 2nd number in the viscosity spec XW-##. 75W-90 will be perfect for an 80W-90 application.
I don't believe SuperTech has any LSD additives.
What is the rule of thumb (or is it not that simple) when choosing a gear oil? I'm also trying to see if I can match the oil choice with some other vehicles my friends have, in order to try and keep overall costs down (buying by the 5 gallon bucket).
My rule of thumb would be match the GL rating the manufacturer specifies (GL-4, GL-5, etc.).
Match the 2nd number in the viscosity spec XW-##. 75W-90 will be perfect for an 80W-90 application.
I don't believe SuperTech has any LSD additives.
Quote
What is the rule of thumb (or is it not that simple) when choosing a gear oil? I'm also trying to see if I can match the oil choice with some other vehicles my friends have, in order to try and keep overall costs down (buying by the 5 gallon bucket).
According to machinerylubrication or AGMA :
KV@40*C of gear oil to be selected = 7000 divided by (square root of V, linear velocity of contacting gears in feet per minute )
What is the rule of thumb (or is it not that simple) when choosing a gear oil? I'm also trying to see if I can match the oil choice with some other vehicles my friends have, in order to try and keep overall costs down (buying by the 5 gallon bucket).
According to machinerylubrication or AGMA :
KV@40*C of gear oil to be selected = 7000 divided by (square root of V, linear velocity of contacting gears in feet per minute )
Originally Posted by badtlc
I don't believe SuperTech has any LSD additives.
As per email from Warren Distribution, ST gear lubes Do Contain LS additive.
I don't believe SuperTech has any LSD additives.
As per email from Warren Distribution, ST gear lubes Do Contain LS additive.
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MolaKule
Staff member
I think what most people refer to as "shock load" (mechanical impulse load) in a drive train is when an engine is revved-up and the manual clutch is released quickly.
No gear lube can prevent damage against an impulse load when the localized stresses exceed the gear material's stress properties. The only thing one can do to minimize shock loads is to not repeatedly over-stress the drive train. The pictures from Spicer and other manf. which show shock load damage is NOT a one time event. Repeated shock loads will eventually cause that kind of failure.
ASTM D7452 (L-42) is the only test I am aware of for shock load testing but I have not seen results for this test which compares mineral verses synthetic oils.
So when people say mineral oil is better at shock loading than synthetic-based gear lubes, I would ask for a comparison test which used ASTM D7452 to prove it.
SWRI has gear and Gear lube tests listed here: https://www.swri.org/industry/lubri.../axle-manual-transmission-fluids-testing .
The reason I use synthetic 75W110 is that it prevents cold weather channeling but yet provides a good thick film for gear teeth and bearings at high temperatures.
No gear lube can prevent damage against an impulse load when the localized stresses exceed the gear material's stress properties. The only thing one can do to minimize shock loads is to not repeatedly over-stress the drive train. The pictures from Spicer and other manf. which show shock load damage is NOT a one time event. Repeated shock loads will eventually cause that kind of failure.
ASTM D7452 (L-42) is the only test I am aware of for shock load testing but I have not seen results for this test which compares mineral verses synthetic oils.
So when people say mineral oil is better at shock loading than synthetic-based gear lubes, I would ask for a comparison test which used ASTM D7452 to prove it.
SWRI has gear and Gear lube tests listed here: https://www.swri.org/industry/lubri.../axle-manual-transmission-fluids-testing .
The reason I use synthetic 75W110 is that it prevents cold weather channeling but yet provides a good thick film for gear teeth and bearings at high temperatures.
Last edited:
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