Synthetics need more additives?

[GMorg]

I noticed in Molacule's write-up on gear oils that synthetic base fluids needed more additives to be formulated. Lubrizol recommendations are similar with about 20% more additive recommended in the final fluid for a synthetic base.

So, are mineral base stocks so much better (excluding temperature related performance) that they don't need the same dose of additives.

 

[GMorg]

Well, from what I can gather for engine oil, some additives have to be increased when used with polar base oils that compete with additives at surfaces. However, Group III and IV oils are not polar so surface competition is not the answer. Perhaps, Group III and IV oils do not "wet" the surface as well and therefor do not lubricate as well as the more polar base oils.

I seem to be posting to myself...

 

[unDummy]

Could it be the 'carrier oil' for the additive?

Since the solvency isn't there with the III or IV base oil, we'll need more additive with its own carrier to mix up well?

I also think that the usually recommended high OCI, or the more aggressive use of the synth, might be a reason to want more additive in the long run. For example, fill for life synthetic vs a shorter change interval mineral oil? Or, 150hp through my mineral gear oil recommended differential(5.8L early circa 1981) vs 400hp through a similar diff requiring synthetic today?

 

[GMorg]

You may be right, but it seems that the recommendations are for the same specification. I'm still lost.

 

[unDummy]

But, it really isn't the same spec. The synthetics will usually operate at a wider temperature range. A mineral 80w90 and synthetic 75w90 are both the same spec GL5. But, they are different.

 

[Tempest]

Originally Posted By: GMorg
I noticed in Molacule's write-up on gear oils that synthetic base fluids needed more additives to be formulated. Lubrizol recommendations are similar with about 20% more additive recommended in the final fluid for a synthetic base.


Can you provide links to these?

 

[GMorg]

Sure...

https://bobistheoilguy.com/forums/threads/gear-tribology-and-lubrication-part-ii.57858/

http://www.zianewmedia.com/portfolio/pdfs/files/lubrizol_anglamol.pdf

 

[GMorg]

I noticed that in Molacule's white paper it is said that synthetics usually have more additives because they are expected to be in service longer. I am curious if that is the whole story. Perhaps synthetics don't "need" more adds. If that is the case, perhaps this situation is why group III fluids are often priced similarly to Group IV fluids. If the additives are a large part of the cost, the two flavors of "synthetic" may approach similar costs.