My apologies to Arco if I have misunderstood his comments.
Anyone is welcome to come on here and engage in a technical discussion and to provide engineering data.
I am not here to butt heads or to engage in personality conflicts (a waste of time) but to provide some background technical information such as:
Gear Lubricants
While the above link was penned in 2003, about the only major changes in gear oil formulations for mineral oils have been the change from Group I to group II and III base oils in gear lubes.
In terms of additive technologies overall, the major changes have been from high sulfur and phosphorus (S-P) Extreme pressure (EP) compounds to a multi-functional phosphorus compound with lower levels of phosphorus and sulfurized esters while still providing excellent wear protection.
In terms of full synthetic gear lubes, some new and proprietary base oils have been introduced to reduce wear with lower levels of EP compounds.
For example in the above link we have this formulation:
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B. A 75W90 Blend [or Para-Synthetic]
9.5% EP additive package
20% 600 Neutral mineral oil [Group I [solvent refined) or II (hydroprocessed) Paraffinic 12.5 cSt@100C]
25% PAO of 4 cSt viscosity
20% PAO of 100 cSt viscosity
2% Pour-Point Depressants
It will have a viscosity of 14.45 cSt and VI of 157.
There is are two main reasons for the inclusion of the PAO's.
1)The PAO 4 is to provide for improved cold weather operation and to prevent channeling. This offers an advantage during cold temperature start-up when channeling can cause temporary lubrication starvation, particularly in splash-lubricated gear drives. Machinery Lubrication's Glossary of terms has a good definition of channeling:
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Channeling
The phenomenon observed among gear lubricants and greases when they thicken due to cold weather or other causes, to such an extent
that a groove is formed through which the part to be lubricated moves without actually coming in full contact with the lubricant....
In addition, oxidation resistance can be improved with the addition of PAO's.
2) In older formulations a Bright Stock was used to improve the Minimum Oil Film Thickness (MOFT) at high gear and bearing temperatures.
Again from Machinery Lubrication's Glossary of terms:
Quote
Bright Stock
A heavy residual lubricant stock with low pour point, used in finished blends to provide good bearing film strength, prevent scuffing, and reduce oil consumption. Usually identified by its viscosity, SUS at 210 degrees F or cSt at 100 degrees C.
It was found that by replacing Bright Stock with a 40 cSt-to-100 cst PAO, higher MOFT and lower temp Pour Points could be achieved.
So the inclusion of PAO's in Blends [or Para-Synthetics] can provide various improvements in finished gear lubes.
