Another informative video! Any videos on friction modifiers? I see some companies like RedLine have Non Slip versions of their GL-5 gear oils and ot looks like the friction modifier is the only difference between a 75w90 and 75w90NS.
A differential starts off with 90w. But aeration cuts the viscosity down, that also cuts down on HP loss. Doesn't air bubbles disrupt the surface tension or oil film on a hypoid gear situation, wouldn't that also lead to gear wear. It seems differential oils use a minute amount of anti-foam added to them. And would a dry lube like molyboledium disulfide and or graphite help in a hypoid gear situation. I got more questions coming. Thx a bunch I have been looking for a channel just like this.
Dry lubes like moly, graphite, and teflon are EP additives that really only see action when the base fluid film has broken down under severe shock loading or other extreme conditions like a combination of high load and high heat(reducing actual operating viscosity). These EP additives do not have very low friction or traction, their purpose is only to prevent damage and wear by cushioning direct metal to metal contact.
Does the PAO have better inherent load capacity at a given true bulk operating viscosity,(say 15cSt mineral at 70c operating temp vs 15cSt PAO at 70c operating temp) or is this a byproduct of the better VI causing an increase in hot viscosity for a given 40c viscosity?(15cST mineral oil at 70C but the PAO is actually 20cSt at 70c) I use 70c as the example so as not to confuse the true in-service viscosity with the standard 40c or 100c "viscosity-grade" measures. Second you say PAG have low traction coefficients, but does this interact with load capacity? I mean is that statement based on equal bulk viscosity or on equal load capacity? To clarify when I say 'bulk' viscosity I mean the low pressure low shear condition normally used for classifying lube viscosity grades, rather than the localized high pressure load carrying viscosity.
Yes. So in general, you're often able to go down an ISO viscosity grade when switching from a mineral to PAO gear oil. By that I mean you could be using an ISO 460 gear oil, then switch to an ISO 320 gear oil, and the two will have equal load carrying capabilities despite the PAO having a lower "true bulk" operating viscosity. To actually discover the load carrying-capabilities of a gear oil you need to do some calculations around EHL (Elasto-Hydrodynamic Lubrication) with some data input from the oil supplier. For your question about PAGs, I'm comparing with a same-viscosity grade PAO gear oil. They'll probably have roughly equal load carrying capacity, but the PAG will typically have a lower traction coefficient. Hope that answers your question!
@@LubricationExplained Mostly. I think my vocabulary limited my the question of PAO load capacity vs viscosity. I was trying to compare equal operating viscosity rather than comparing ISO viscosity-grade. eg an iso320 PAO with VI-129 and a mineral ISO460 with VI-94 will both be 30cSt at 100c. So if the operating temp is 100c the two oils would have the same "actual operating viscosity"(phrasing used by SKF) despite being different iso viscosity grades. And that brings me to the original question, with each at an operating temperature of 100c and the same actual operating viscosity of 30cSt would a PAO have substantially more load capacity than the mineral?
IN a nut shell PAO oils are better than group 1,2 and 3 from my understanding. If I cannot find PAO gear oil, could I use an engine oil? 10W40 being similar viscosity index as 75w-90. I have straight cut gears, ball bearings, chain drive with tensioner, high speed low load and high load low speed straight cut gears, oil squirters for all gear mesh intersections. I also want to make the straight cut gears as quiet as possible but at the same time do not require the oil to be thick or want it to stick to the gears. Sorry for all the questions/ comments. Love your videos. I should just do testing I suppose.
There are a fair few gear oils that are really just cut-back engine oils - so you'd probably be okay. But from all your comments it seems like you're chasing reasonably high performance - I'd suggest looking toward some of the industrial gear oils, where PAOs and PAGs are reasonably common.
Finally find some one who can make sense of this!
Glad you found it useful!
@@LubricationExplained Ok I will be asking you plenty of questions! Inquiring minds need to know!! ;)
Another informative video! Any videos on friction modifiers? I see some companies like RedLine have Non Slip versions of their GL-5 gear oils and ot looks like the friction modifier is the only difference between a 75w90 and 75w90NS.
I just asked for one of these not realizing you already had one lol, now we just need one on trans fluid
A differential starts off with 90w. But aeration cuts the viscosity down, that also cuts down on HP loss. Doesn't air bubbles disrupt the surface tension or oil film on a hypoid gear situation, wouldn't that also lead to gear wear. It seems differential oils use a minute amount of anti-foam added to them. And would a dry lube like molyboledium disulfide and or graphite help in a hypoid gear situation. I got more questions coming. Thx a bunch I have been looking for a channel just like this.
Dry lubes like moly, graphite, and teflon are EP additives that really only see action when the base fluid film has broken down under severe shock loading or other extreme conditions like a combination of high load and high heat(reducing actual operating viscosity). These EP additives do not have very low friction or traction, their purpose is only to prevent damage and wear by cushioning direct metal to metal contact.
Does the PAO have better inherent load capacity at a given true bulk operating viscosity,(say 15cSt mineral at 70c operating temp vs 15cSt PAO at 70c operating temp) or is this a byproduct of the better VI causing an increase in hot viscosity for a given 40c viscosity?(15cST mineral oil at 70C but the PAO is actually 20cSt at 70c)
I use 70c as the example so as not to confuse the true in-service viscosity with the standard 40c or 100c "viscosity-grade" measures.
Second you say PAG have low traction coefficients, but does this interact with load capacity? I mean is that statement based on equal bulk viscosity or on equal load capacity?
To clarify when I say 'bulk' viscosity I mean the low pressure low shear condition normally used for classifying lube viscosity grades, rather than the localized high pressure load carrying viscosity.
Yes. So in general, you're often able to go down an ISO viscosity grade when switching from a mineral to PAO gear oil. By that I mean you could be using an ISO 460 gear oil, then switch to an ISO 320 gear oil, and the two will have equal load carrying capabilities despite the PAO having a lower "true bulk" operating viscosity.
To actually discover the load carrying-capabilities of a gear oil you need to do some calculations around EHL (Elasto-Hydrodynamic Lubrication) with some data input from the oil supplier.
For your question about PAGs, I'm comparing with a same-viscosity grade PAO gear oil. They'll probably have roughly equal load carrying capacity, but the PAG will typically have a lower traction coefficient.
Hope that answers your question!
@@LubricationExplained Mostly. I think my vocabulary limited my the question of PAO load capacity vs viscosity.
I was trying to compare equal operating viscosity rather than comparing ISO viscosity-grade. eg an iso320 PAO with VI-129 and a mineral ISO460 with VI-94 will both be 30cSt at 100c. So if the operating temp is 100c the two oils would have the same "actual operating viscosity"(phrasing used by SKF) despite being different iso viscosity grades.
And that brings me to the original question, with each at an operating temperature of 100c and the same actual operating viscosity of 30cSt would a PAO have substantially more load capacity than the mineral?
IN a nut shell PAO oils are better than group 1,2 and 3 from my understanding. If I cannot find PAO gear oil, could I use an engine oil? 10W40 being similar viscosity index as 75w-90. I have straight cut gears, ball bearings, chain drive with tensioner, high speed low load and high load low speed straight cut gears, oil squirters for all gear mesh intersections. I also want to make the straight cut gears as quiet as possible but at the same time do not require the oil to be thick or want it to stick to the gears. Sorry for all the questions/ comments. Love your videos. I should just do testing I suppose.
There are a fair few gear oils that are really just cut-back engine oils - so you'd probably be okay. But from all your comments it seems like you're chasing reasonably high performance - I'd suggest looking toward some of the industrial gear oils, where PAOs and PAGs are reasonably common.
Lots of people do this in the power sports world. Bikes, atv's SxS's, even compact & sub compact tractors.
Never heard of a problem using these subs.