Metallocene PAO (mPAO) verses conventional PAOs (cPAO)

MolaKule

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Metallocene PAO (mPAO) verses conventional PAOs (cPAO)
By MolaKule

Sometimes a White Paper or technical article comes about from a question by one of our astute BITOG members and this is one of those.

Note: cPAO's are NOT to be confused with conventional mineral oils. It is simply a way to differentiate between these two types of PAO's.

mPAO's are produced utilizing a metallocene catalyst. This novel catalyst allows the base oil manufacturer to control how the linear alpha olefins react.

mPAO's consist of a range of high viscosity PAOs that have been designed to provide ultra high viscosity indicies, improved low temperature fluidity and combined with shear stability equal to or better than standard cPAOs.

(For a discussion of conventional PAO's, See Section II: Synthetic Base Oils group IV and V at: https://www.bobistheoilguy.com/ A Review of Mineral and Synthetic Base Oils)

In chemistry, a metallocene is any of a group of organometallic compounds that consist of a metal atom bonded between two cyclopentadienyl (or similar aromatic) rings in a sandwich structure, used especially as catalysts in polymer synthesis.

Molecularly, mPAO's have a uniform comb structure that lacks short side chains while cPAO's have long and short side chains in a random orientation on either side of the backbone.

While cPAO's are in no way inferior, mPAO's offer certain advantages over cPAO's.

Some of the advantages touted for mPAO's are:
1. Higher viscosity indices
2. Better low temperature fluidity
3. Enhanced film thickness at higher temperatures reduce wear
4. Lower foaming tendencies
5. Lower traction properties which translate to greater energy efficiency

Most mPAO's are available in 65 to 300 cSt@100C viscosities.

In gear oil formulations, approximately 5-7% of an mPAO gives rise to higher film thicknesses at elevated temperatures and can replace conventional thickeners, such as polyisobutylene's, which can reduce cold temperature performance.

In low viscosity motor oil formulations, approximately 0.5-3% of an intermediate viscosity mPAO gives rise to higher film thicknesses at elevated temperatures and can reduce the levels of VII's needed to maintain viscosity and film thicknesses.

Some of the major manufacturers of mPAO's are DuraSyn (INEOS), SpectraSyn Elite (Exxonmobil), and Synfluid (Chevron Phillips).
 
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Joe Gibbs Driven oils are big on this stuff. They claimed to have great NASCAR oils that maintain HTHS during drafting.
 
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Great write-up. I'm growing more fond of mPAO and wish more blenders would use it.

What I've wondered is where it could suitably be used in place of conventional (homopolymer, trimer, etc...) PAO. Take Mobil 1 EP 5w-30, for example, which is 30% homopolymer PAO. What if you replaced that with 10-15% of 65 cSt mPAO? Would the performance be similar, better, or worse? I imagine cost is the main reason it's not commonly used.
 
XOM points out that mPAO base stock is seeing an increased demand in wind turbines as they become larger and larger …
 
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Base oils or used in place of vii vm's, or used to thicken thinner base oils to reach the SAE grade??? Seems pretty thick.



I guess Mobil understand higher film strength/thickness.


When I think of base oil, I think of the 60-80% base oil in the formula. If its a 5-10% 'correction fluid', I wouldn't care to call it a base.

I guess saying, "we use mPAO base oils" is impressive, when compare to saying "we use
I wonder how it performs when compared to the polymer esters like Ketjenlube. Maybe similar but at a different price point or dosage amount. I vaguely remember ketjenlube needing 10-20% as a correction fluid to boost formulated fluids performance.
 



Base oils or used in place of vii vm's, or used to thicken thinner base oils to reach the SAE grade??? Seems pretty thick.




When I think of base oil, I think of the 60-80% base oil in the formula. If its a 5-10% 'correction fluid', I wouldn't care to call it a base.

A different base oil of a different viscosity may be used to enhance performance or to bring a formulation to a specific viscosity.
I wonder how it performs when compared to the polymer esters like Ketjenlube. Maybe similar but at a different price point or dosage amount. I vaguely remember ketjenlube needing 10-20% as a correction fluid to boost formulated fluids performance.
You don't use Ketjenlube polymer esters as base oils as they are too expensive. You use them as an additive component when you need need to reduce or to drop an organometallic anti-wear component (such as ZDDP) from your formulation. An example is some hydraulic oils where heavy metals are not to be included.
 
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