The enhanced oxidative stability of mPAO base stocks tech video

mPAO is not really a base stock. It's an alternative type of viscosity-index improver (VII). ExxonMobil is probably right that it's more oxidatively stable than a conventional VII.

It experiences temporary and permanent shear like a conventional VII does; therefore, it would be misleading to think of it as a "neat" (VII-free) base stock.
 
Originally Posted by Gokhan
mPAO is not really a base stock. It's an alternative type of viscosity-index improver (VII). ExxonMobil is probably right that it's more oxidatively stable than a conventional VII.

It experiences temporary and permanent shear like a conventional VII does; therefore, it would be misleading to think of it as a "neat" (VII-free) base stock.


I was curious about that too. So blends that contain mPAO are likely using it as an additive or for VI purposes.
 
MPAO is used in many high end race oils at 10-30% concentration to improve oxidation resistance, move the flashpoint higher, and improve shear stability. I know the concentration in the oil used in many NASCAR cup engines and after 500 miles at 8000+ rpm and 700+hp, the KV100 is still rock solid. These oils also contain >10% POE.
 
Originally Posted by buster
I was curious about that too. So blends that contain mPAO are likely using it as an additive or for VI purposes.

I think mPAO is primarily used as an alternative to a conventional VII. It temporarily and permanently shears somewhat, perhaps less than a conventional VII does, depending on its molecular weight. I wouldn't expect it as to be as thermally stable as a regular, low-molecular-weight PAO, but it should be more thermally stable than a conventional VII. However, it probably costs a lot more than a conventional VII. If it didn't, chances are that everybody would be using it for multigrade-oil formulations.
 
mPAO is a base oil, it's just used in small amounts.
 
Originally Posted by buster
mPAO is a base oil, it's just used in small amounts.

OK, you're right -- it has a very low pour point. SpectraSyn Ultra high-viscosity PAO is a lot less shear-stable than SpectraSyn Elite mPAO.

I now understand why mPAO is not desirable in engine-oil formulations. Unlike a VII it doesn't shear and lower the viscosity in the cold-cranking simulator (CCS) test, which is a high-shear test; therefore, an oil formulated with more than a few percent of mPAO would fail the W rating of its SAE viscosity. It is used in racing-oil formulations because they don't care about the W rating for them.

ExxonMobil synthetic-blending guide has some examples of engine-oil formulations with small mPAO amounts. You can see that even a small amount of mPAO increases the CCS significantly without boosting the viscosity index sufficiently, which wouldn't be the case for a VII.

https://www.exxonmobilchemical.com/...lubricant-base-stocks-formulations-guide

Chevron makes it as well.

https://www.stle.org/images/pdf/STL...AOs%20High%20Viscosity%20Base%20Oils.pdf
 
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So, forgive my non-chemist mind here, but looking at page 5 of the Chevron PPT would lead me to believe that any oil with a VI above 170 is using a good portion of mPAO? This would then lead one to reason that mPAO is the main reason we typically see Noack increase WRT VI.

Do oils with regular PAO do better on Noack test than mPAO? Not that I buy into all of it, but that information would be good for the GDI folks who think Noack is the end-all, be-all of oils for their engines.
 
They are on the thick side too … which is what they were comparing. Curious if anyone knows the percentage that Driven Racing is using ?

We talk cars, SUV, LT's and stuff like that … but a gearbox on a cement grinder lives a tough life … hence often used by Mobil Industrial Lubricants division.
 
Originally Posted by SubieRubyRoo
So, forgive my non-chemist mind here, but looking at page 5 of the Chevron PPT would lead me to believe that any oil with a VI above 170 is using a good portion of mPAO? This would then lead one to reason that mPAO is the main reason we typically see Noack increase WRT VI.

Do oils with regular PAO do better on Noack test than mPAO? Not that I buy into all of it, but that information would be good for the GDI folks who think Noack is the end-all, be-all of oils for their engines.

Oh, no, I doubt any engine oil, other than racing oils, uses mPAO. Even if it does, the amount would have to be very small to still meet the W spec, and you wouldn't see much effect other than a small boost in the viscosity.

You obtain a higher VI by putting more VII. This also requires the base oil to be thinner, which in turn increases the Noack. It's not necessarily bad news for GDI engines, as it's the base-oil quality, not the Noack, that really matters since the intake-valve deposits are caused by the liquid PCV mist, not distilled vapor.
 
MPAO is used in some "street" oils outside of the racing realm. The concentration is <20%. In the racing world though, the main use is to improve shear stability and increase the flash point. The bulk of those oils are group III for better additive response.
 
Originally Posted by RDY4WAR
MPAO is used in some "street" oils outside of the racing realm. The concentration is div>

Again, the problem with using mPAO in multigrade oils is the CCS viscosity. They don't even bother to list the CCS viscosity in the mPAO datasheets. With 20% mPAO I doubt you can formulate anything with a cold range lower than 20W, and I don't know even if that is possible.
 
Originally Posted by Gokhan
Originally Posted by RDY4WAR
MPAO is used in some "street" oils outside of the racing realm. The concentration is div>

Again, the problem with using mPAO in multigrade oils is the CCS viscosity. They don't even bother to list the CCS viscosity in the mPAO datasheets. With 20% mPAO I doubt you can formulate anything with a cold range lower than 20W, and I don't know even if that is possible.


I feel like if you have an application that needs the high heat and shear stability of mPAO, you probably aren't too concerned with CCS.
 
Originally Posted by RDY4WAR
I feel like if you have an application that needs the high heat and shear stability of mPAO, you probably aren't too concerned with CCS.

It's true.

However, the CCS (low-temperature, high-shear) and MRV/Brookfield (low-temperature, low-shear) tests are mandatory for any xW (or xW-y) viscosity in the SAE J300 standard, regardless of the application, such as racing. If the SAE viscosity grade is a monograde without the W rating, these two tests are not required. VIIs increase the low-shear viscosity MRV but don't increase the high-shear viscosity CCS because they shear under high shear rates. The CCS spec is a lot lower than the MRV spec; therefore, you need a VII, which shears to lower the CCS, to formulate a W-rated oil.

For gear oils SAE J306 and SAE J2360 apply, and there is no CCS spec. However, there is a Brookfield viscosity (low-temperature, low-shear viscosity) spec. Nevertheless, since there is no CCS spec, this allows the use of mPAO even for SAE xW gear oils.
 
High Performance Lubricants has a 10w-50 motorcycle oil that contains a relatively high concentration of mPAO, no VII, and it passes the 10w-50 CCS without a problem. Driven DI30 and DI40 also contain mPAO and pass without a problem.
 
Noticed Driven had a street rod 10w40 with mPAO … perhaps 10w is it on winter games with mPAO
 
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