Group V ester versus Group IV PAO - head to head

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Originally Posted By: Tempest
Quote:
Diester rock for automotice use in my opion.

Not good for seals.


This is interesting. I'm not quite sure what to make of it.

Someone wrote in another forum in 2001:

The problem is that PAO (polyalphaolefin) will harden and shrink seals.
Various seal-swell additives and an addition of an ester base will
help to alleviate seal hardening. In an older vehicle, the seals may
already be borderline ready to leak, and the PAO will shrink the seals
enough to cause leaking before the ester and additives counteract the
PAO. I lot of folks who have had leakage problems have said that they
eventually stopped (e.g. the seal shrinkage was eventually
counteracted).
With newer seals, this isn't much of a problem.

I found an excellent piece (click on "Synthetic Oil Notes in the TOC):
http://www.swedishbricks.net/700900FAQ/Fuel-LubricantData1.html

"1. Synthetic Base Stocks. Group IV base stock is made of PAO and was
for a while the only base used in synthetic oil until Group V (Esters)
came along. PAO has a property of shrinking rubber gaskets, and when
older cars were switched the leaking was generally due to this fact.
Cars with new gaskets that used PAO-based oils from the beginning did
not encounter shrinkage or leakage. The newer and the better synthetic
oils began to incorporate a new base stock (group V -Esters) that helped
to keep the rubber from shrinking."

It also states that the third synthetic base oil in Mobil 1
(Tri-Synthetic) is alkylated napthalene.

...

**Some** folks have had leaks occur when they used synthetic oils
for the first time in high mileage engines. The cause has
often been attributed to "false seals" being flushed out by
the "higher detergency" of synthetic oils. My point was
that the real reason was because of the tendency of a poly-
alphaolefin (PAO) base oil to harden seals. A **borderline**
seal may start to spring leaks, which often go away as the
other ingredients counteract the hardening. A higher
mileage engine may have seals that are in a pretty good
condition, and it most likely won't leak. However - there
are many vehicles that aren't meticulously maintained, and
in many cases their seals may on the borderline of leaking
and will be pushed over the edge if synthetic oil is used.

My only beef is with the "false seals" theory that has been
prevalent [in this forum and elsewhere].

# # # # #

Most synthetic oils contain polyalphaolefin (PAO), including Mobil 1,
Valvoline SynPower, Amsoil, etc. Red Line contains only a polyol
ester base oil.

PAO has a tendency to harden/shrink rubber gasket materials. This led
to seal shrinkage/hardening, which then led to leaks springing up.
I found a few more references to this:

Techincal info from a Pennzoil distributor in Australia:
/www.home.aone.net.au/oilandenergy/proddocs/sohistry.htm>

"Oil consumption was a severe problem with the original Mobil 1. The
product as originally formulated had a slight shrinking effect on
seals. The seal effect combined with the low product viscosity led
to excessive leakage. There were extensive complaints that the oil
would not stay in the engine. Incorporation of some ester into the
formulation corrected the seal problem and the viscosity grade was
raised to 5W-30. These two changed corrected the leakage problem
but the reputation took longer to correct."

...

Neither of these articles mention anything about "marginal" seals,
but if PAO has a tendency to harden seals, it stands to reason that
the effect would be more pronounced if the seals were already
hardened to begin with. I'm pretty sure that no finished automotive
motor oil today contains only PAO as its base, and there should be
no problems using a PAO-based motor oil in a lower mileage engine.
There may or may not be leakage problems in higher mileage engines.
I've used Mobil 1 in engines of varying ages, and haven't had any
leakage problem due to it use. However - some folks have reported
leakage problems, and I was just trying to explain the mechanism
behind that leakage.

$ $ $ $ $ $

[However, someone else wrote:]

Esters suffer the further disadvantage of greater seal-swelling tendencies
than hydrocarbons; so, caution must be exercised in using them in applications
where they may contact elastomers designed for use with mineral oils.

Polyalphaolefins are the most widely used synthetic lubricants in the U.S. and
Europe. They are made by combining two or more decene molecules into an
oligomer, or short-chain-length polymer.

PAOs are all-hydrocarbon structures, and they contain no sulfur, phosphorus or
metals. Because they are wax-free, they have low pour points, usually below
-40°C. Viscosity grades range from 2 to 100 cSt, and viscosity indexes for all
but the lowest grades exceed 140.
PAOs have good thermal stability, but they require suitable antioxidant
additives to resist oxidation. The fluids also have limited ability to dissolve
some additives and tend to shrink seals. Both problems can be overcome by
adding a small amount of ester.

Dibasic acid esters are synthesized by reacting an acid and an alcohol.
Diesters have more varied structures than PAOs, but like PAOs, they contain no
sulfur, phosphorus, metals or wax. Pour points range from -50 to -65°C.
Advantages of diesters include good thermal stability and excellent solvency.
They are clean-running in that they tend to dissolve varnish and sludge rather
than leave deposits. In fact, diesters can remove deposits formed by other
lubricants.
Proper additive selection is critical to prevent hydrolysis and provide
oxidative stability. In addition, chemically resistant seals are recommended.

Polyol esters, like diesters, are formed by the reaction of an acid and an
alcohol. "Polyol" refers to a molecule with two alcohol functions in its
structure; examples include trimethylolpropane (TMP), neopentylglycol (NPG),
and pentaerythritol (PE).
Polyol esters contain no sulfur, phosphorus or wax. Pour points range from -30
to -70°C and viscosity indexes from 120 to 160. The fluids have excellent
thermal stability and resist hydrolysis somewhat better than diesters. With the
proper additives, polyol esters are more oxidatively stable than diesters and
PAOs. Seal-swell behavior is similar to that of diesters.
Alkylated aromatics are formed by the reaction of olefins or alkyl halides with
an aromatic material such as benzene. The fluids have good low-temperature
properties and good additive solubility. Viscosity index is about 50 for fluids
with linear molecules and zero or lower for fluids with branched side chains.
Thermal stability is similar to that of PAO, and additives are required to
provide oxidative stability.

Polyalkylene glycols (PAGs) are polymers of alkylene oxides. Lubricant
performance and properties of a particular PAG depend on the monomers used to
manufacture it, molecular weight, and the nature of the terminal groups. Thus,
a wide range of properties is possible.

In general, PAGs have good high-temperature stability and high viscosity
indexes, and they can be used over a wide temperature range. They exhibit low
deposit formation and tend to solubilize their decomposition products. Like
other synthetics, PAGs require additives to resist oxidation.

Phosphate esters are synthesized from phosphorus oxychloride and alcohols or
phenols. They are used both as base oils and as antiwear additives in mineral
and synthetic lubricants. Thermal stability is good, and pour point ranges from
-25 to -5°C. However, viscosity index is extremely low, ranging from 0 to -30,
which limits their high-temperature capabilities.

+++

Note that the synthetics are free from waxes and impurities, do better at high
and low temps, have good resistance to oxidation, and typically have very high
viscosity indexes.

Overall, I think these qualities allow lighter viscosity oils to behave like
wide range multigrade oils with fewer 'STP like' viscosity modifiers. These
plastics, polymeric viscosity modifiers, can burn and cause piston ring
deposits... and failure. They are high Ash, and this is why the old 10W-40
mineral oil products cause engine failures.

Newer VI modifiers are better, but they still shear in high stress
applications. Thats why when you drive a 20W-50 mineral oil hard, it may not
protect the engine as well as a 5W-30 or 10W-40 synthetic...or why a 0W-30
synthetic will protect better than a 10W-30 mineral oil... and start in -60
temperatures, pump immediately to protect engine parts, and allow a few
percentage points of horsepower or fuel efficiency.

In addition, synthetics or VHVI hydrocracked mineral oils may allow the oil
engineers to use fewer additives and still have longer addditve life since the
base stock has few corrosive impurities.
 
I'm just a beginner, but I think after reading the above, I'm going to skip the PAO oils (like Amsoil) since they apparently have a tendency to shrink seals--counteracted only by the addition of esters into the PAO oil.

Aside from Group III Pennzoil Platinum, I'll probably just try Renewable Lube's Bio-Syn and the Red Line oil, since they're both Group V esters.

Groups 3 and 5 for me :)

And I came into this with a totally open mind, willing to try any oil.
 
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I don't know what Mobil 1 15W-50 is group wise, but I suspect III/IV/V mix. I have a Toyota 4 cyl pickup with 300,000 miles and 250,000+ of those miles are with Mobil 1 15W-50. It does not use a drop of oil between OCI, the level on the dip stick does not change.

My wife has a Chevrolet Cavalier 4 cyl with 202,000 miles and every one of those miles are Mobil 1 15W-50. It does not use a drop of oil between OCI, the level on the dip stick does not change.

Both the truck and the car are getting better than the origional estimated mileage.
 
Originally Posted By: Built_Well
I'm just a beginner, but I think after reading the above, I'm going to skip the PAO oils (like Amsoil) since they apparently have a tendency to shrink seals--counteracted only by the addition of esters into the PAO oil.

Aside from Group III Pennzoil Platinum, I'll probably just try Renewable Lube's Bio-Syn and the Red Line oil, since they're both Group V esters.

Groups 3 and 5 for me :)

And I came into this with a totally open mind, willing to try any oil.


Quote:
Group IV base stock is made of PAO and was
for a while the only base used in synthetic oil until Group V (Esters)
came along. PAO has a property of shrinking rubber gaskets, and when
older cars were switched the leaking was generally due to this fact.


This is total and unadulterated TRIPE. Something some dude posted on a Volvo site is now taken as the truth. Dude it's the INTERNET! Esters didn't suddenly waltz up and replace PAO. Pure rubbish.

I now have thousands of customers, and I've been using Amsoil myself for over 10 years solid. Nothing but. No leaks. Zero.

I'm just going to politely suggest you keep learning.

And just for info to the above, Redline oils have a large percentage of PAO. 100% ester simply does not work, either.
 
Originally Posted By: Pablo
This is total and unadulterated TRIPE.

Pablo, I am going to have to disagree with you on that. I believe it to be well understood that one of the characteristics of PAO oils as commonly used in motor oils is that they tend to shrink seals. This is not necessarily a problem as it is easily counteracted by adding swelling agents, and an excellent oil can result. However, I also believe that one problem some of the early synthetics was that this was not well understood, and in fact seal-shrinking tendencies were present in some of those early oils, resulting in many oil leaks and the (now) myth that synthetic oils can cause leaks.

While it is definitely true that PAO oils can be first rate, I do believe it is an advantage of esters that they do not require the chemical enhancement of seal swelling additives.

I would also ask what information you have about the PAO content of Red Line's oils.
 
My understanding is that the early Amsoil formulations (and maybe Mobil) were di-ester based. This causes seals to swell larger than they should which caused them to wear. This was not a problem as long as the di-ester oils continued to be used, but as soon as something else was put in, the seals would shrink and cause a leak. I believe this is were the idea that "you can't go back" came from.

I also believe that PAO in and of itself does not cause seals to shrink, but rather it does not contain the chemicals that the seals are designed to have for seal swell. In other words, they are seal neutral.

Adding esters to the mix makes seals happy and maintains them at the proper size.
 
Actually the early synthetic oils that leaked were diesters, and they were degrading and blowing right by seals. Both PAO's and some esters have effects on seals - as do conventional oils which generally will dry and harden seals. None of this is that simple.

As for Redline, buster posted a statement by the head of Redline several years ago. Let me dig around.
 
Originally Posted By: Built_Well
I'm just a beginner, but I think after reading the above, I'm going to skip the PAO oils (like Amsoil) since they apparently have a tendency to shrink seals--counteracted only by the addition of esters into the PAO oil.
Your understanding of this subject is a gross oversimplification. PAO, POE, and AN all provide unique properties that, when combined, will deliver a precisely formulated lubricant that meets a specific set of performance criteria. Variables that are fine-tuned by the use of multiple synthetic basestocks include viscosity index, pour point, traction, air release and foaming, viscoelasticity, elastohydro-dynamic film thickness at high temperature, stability and miscibility with regard to various additives, shear stability, hydrolytic stability, thermal and oxidative stability, solvency, volatility, elastomer compatability, etc, etc, etc. BTW, alkylated napthalenes are also API Group V.
 
BerndV makes another good post, keeping the ship from completely crashing into the shore. Same with Pablo. I don't even need to add input, just agreement.
 
Originally Posted By: JAG
BerndV makes another good post, keeping the ship from completely crashing into the shore. Same with Pablo. I don't even need to add input, just agreement.


Maybe so, but they're not defending their position very well. After reading
the other forum's posts about PAOs and esters, I'm still very skittish about
adding primarily PAO-based oils to my car.

I don't have a financial stake in any of the oils, whether they're Group III, IV, or V, so I know I came open-minded to the debate. In fact, on some days,
I would compliment Group IV oils when I learned something positive about them, and on other days I'd applaud Group V.

I'm still uncertain about my next choice of oils, but much more cautious now about Group IV PAOs.

I guess it would be nice if Doctor Haas weighed in here, because I know he is a very smart person. But I'm also sure the Doctor is a very busy person with many responsibilities.
 
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Quote:
I'm still very skittish about
adding primarily PAO-based oils to my car.


You have got to be kidding. It's over 30 years old in "in field" usage. If anything ..some "next evolution" will supersede it ..but none has come to pass at reasonable expense in the cost:benefit end of stuff.

It's not like it's uncharted territory.
 
Originally Posted By: Gary Allan
Quote:
I'm still very skittish about
adding primarily PAO-based oils to my car.


You have got to be kidding. It's over 30 years old in "in field" usage. If anything ..some "next evolution" will supersede it ..but none has come to pass at reasonable expense in the cost:benefit end of stuff.

It's not like it's uncharted territory.


Well, cigarettes have been around for a long time, too ;-)

Just because something's been around a long time doesn't automatically mean it's good for you.

Look at Slick 50 and the Lucas Oil Treatment study on this very web site :)

I, and I'm sure many others, just don't know about PAO IV.

I'd like to think good things about PAOs, but cigarette smokers probably think good things about Winston cigarettes :)
 
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Yes, I'm serious, and I've been very polite.

As mentioned, I'm trying to decide what my next oil will be: a PAO or an ester :)
 
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What don't you understand though? You are just stating things that have no basis in anything. Read what Bernd said above. It's a balance of different base oils. They all have +'s and -'s.

Quote:
AMSOIL views synthetic base oils the same as it views additives, with each having its own set of unique properties. AMSOIL engineers its lubricants with the synthetic base oil or combination of base oils best suited to a specific lubricant’s application demands (gasoline, diesel, racing, transmission, gear, extended drain, extreme temperature, etc.).


The above sums it up. No need to continue discussing IMO. It's very simple.
 
Buster, you're not being very polite when you say I'm {quote} "just stating things that are off the wall."

I thought this site was about honest debate? And I still believe it is :)
 
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Well, thanks for editing your original remark from I'm "just stating things that are off the wall" to something a little nicer.

Anyhow, I'm currently using Group III Pennzoil Platinum, but think I'll try Group V RLI Bio-Syn next.
 
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Come on,boys! It's all just "awl" and we dump it every few thousand miles. Lol.
 
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