Built_Well
Thread starter
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.
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.