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For all you "Johnny Skepticals" on Yamaha oil, filters, etc.
The basic message is change your oil often with a high quality product that meets the engine manufacturer's recommended rating.
This excerpt is from a small engine forum:
--------------------------------------------------------------------------------------
From: monte350v8 [mailto:mewood@eastex.net]
Sent: Sunday, March 16, 2003 10:22 AM
Subject: [Kohler and Onan Engine Club] Motor Oil 101
Motor Oil: The myths, facts, and mysteries of the slippery stuff that keeps your engine happy.
Here's the bottom line when it comes to motor oils: you really can't
go wrong by following the recommendations given in your owner's
manual. Your engine's maker has dyno-tested its engine with a
crankcase full of the specified oil, or one with the same American
Petroleum Institute (API) rating. You can be sure that particular
oil will do the job. Will it do the job better than any other oil?
Will it do the job if the engine is no longer as its manufacturer
made it? Not necessarily, as you will learn by reading further.
The API's ratings once went from 'SA' (guaranteed to be oil) through
the alphabet to 'SE' and was extended to 'SE/CC' (you cant drive a
nail through a film of this stuff.) Today the API has fewer
performance grades, only 'SH' and 'SG' for spark-ignition engines,
with an 'SH/CD' rating for oils good enough to be used in passenger-
car diesels. The motor oils bearing these API markings have been
test-certified for today's engines, which are in turn constructed
with these oils in mind.
You should be aware that motor oils are now being compounded not just
for lubrication, but to improve fuel economy as well. Oils have
always been compounded with a thought for fluid drag; this is the
first time its been made a priority. The API has two economy
ratings: "energy conserving" for motor oils that yield a 1.5%
reduction in fuel consumption as compared with a reference
oil; "energy conserving II" is an oil that provides a 2.7% drop in
fuel consumption.
As you might expect, energy-conserving oils drag reduction benefits
also show up as increased horsepower. Both thermal and mechanical
losses diminish the power liberated in the combustion process on its
way to the output shaft. The work of pumping air in and out of the
engine accounts for the majority of the mechanical losses. The rest
is mostly lost to fluid drag on the piston, which is, all other
things being equal, largely a function of oil viscosity.
Friction exists even in the absence of actual contact between opposed
surfaces. The cylinder wall's oil film normally prevents it from
being touched by the piston; it is a source of friction itself, if we
take that to mean a resistance to relative motion. Millions of
molecules on each side of the gap try to stick together and get
pulled apart. The sum of millions of molecule's minute resistance to
separation comprises viscous drag, the source of most friction in a
running engine.
Viscosity aside, the most important property of oil is that it
be "oily." Introducing any liquid between a piston and cylinder
wall, for example, will reduce friction between the two surfaces.
The degree to which friction will be reduced is, broadly speaking, a
function of the liquid's viscosity. But maple syrup and motor oil of
essentially identical viscosity do not lubricate equally, as you
discover by rubbing samples of each between thumb and forefinger.
If "oiliness" were the only quality to be considered in choosing
motor oils, we'd be squeezing all ours from castor beans. Castor
oil, the smell of which once perfumed the air at motor races, is the
oiliest of oils and it remains in some respects the supreme
lubricant. It does oxidize too readily, however, forming ring-
sticking gums and varnishes, and daubing fouling deposits on spark
plugs. In a running engine, castor oil goes right to work gluing
piston rings in their grooves and slathering gum and varnish
everywhere. You wouldn't want it in any engine that can survive
without its help.
But castor oil, a mixture of ricinoleic and triricinoleic glycerides,
plus 10-12% of other fatty acids, remains one of the best lubricants
for 2-stroke racing engines. Castor oil clings to metal with such
tenacity it cannot be removed except by machining. It is an
exceptionally effective film lubricant.
Oil forming a hydrodynamic wedge between surfaces keeps pistons and
bushing-type bearings from metal-to-metal contact. Viscosity pulls
the oil between a moving piston and its adjacent cylinder wall, or a
shaft and a bearing, and pressurizes the gap. The pressure increases
with viscosity and speed, and a well-designed engine almost totally
prevents scrubbing contact.
The qualifying "almost" is needed because hydrodynamic action is not
present in an engine at start-up, and it collapses around the pistons
and rings at the end of their strokes. Under these conditions, parts
are protected only by film lubrication, which is provided by the
bipolarity of the oil molecules. The molecules behave like tiny
magnets and adhere to ferrous metals and each other.
One of the great improvements in motor oils came circa 1950, when the
detergent/dispersant additives developed for diesels came into more
general use. Alas these brought with them unfortunate consequences
for old, high-mileage engines. In those, the detergents sometimes
dislodged great clots of oxidized oil filth to clog filters and oil
passages. Engine failures caused by detritus liberated in this
manner put additive oils in bad repute, with the results that some
people still buy and use straight non-additive oils.
The first oil additive was probably the spoonful of sulfur old-time
truck operators tossed into axle and transmission housings. The
sulfur reacted with gear-tooth steel to give the gears an iron
sulfide film. The film was important because the relative speeds
between meshing gears is too low to form a fluid wedge strong enough
to resist the extremely high gear-tooth loads.
Engines also have points at which loadings can exceed the carrying
capacity of the fluid wedge. Take the tiny contact area between the
exhaust cam and follower, for example. The load there rises to
roughly 1500 pounds for every ounce of valve train weight at high
engine speeds. Full throttle adds 80 pounds of load for every square
inch of valve head area, meaning the load focused on the cam/follower
can reach pressures in the order of 20,000 pounds per square inch.
Cams would have to spin much faster than they do (half crank speed)
to work up a fluid wedge capable of carrying such high loadings. So
the job has to be done with film lubrication, which means more
viscous oil, one with special properties (castor) or an extreme
pressure (EP) additive. It's obvious that film lubrication is
important, where some of us go wrong is in leaping to the conclusion
that those who compound motor oils have overlooked this very point.
Most parts dealer's shelves usually have a selection of additive
liquids that claim to be a supreme cure all oil additive. This stuff
reduces the friction in your wallet enough to make money slip out of
it, but may not do anything else. About the best you can hope from
additives is that it will either be more of the same additives
already in good-quality motor oils, or at least not get in the way of
the additives that can do something useful.
Film-condition additives usually are chemically and/or thermally
reactive. The sulfur- and phosphorus-based compounds react with iron
to form slippery iron sulfides, as previously noted, or wear-
resistant iron phosphates. Fatty acids, like those in castor oils,
react with iron to make low-friction iron soaps.
Thermally reactive "liquid metals" like molybdenum dithiophospate,
are oil-soluble chemical compounds; molybdenum sulfide, on the other
hand, is a cheap dry-slide lubricant sometimes used in greases. If
you put MOS or other dry-slide lubricant powders like colloidal
graphite in motor oil, these solids may settle or filter out. Worse,
they may become a barrier blocking the more effective reactive
additives.
The liquid metals dissolve in oil, like salt in water, and remain in
solution at all normal engine-operating temperatures. But when
friction heats the liquid metal compounds they come apart and their
metallic component is plated on the hot spot. This stops the most
potent, least obvious wear process in today's filter-protected
engines: direct, scrubbing contact between a cam and follower, gear
teeth, etc. This contact results in wear largely due to friction
welding: Friction melts pinpoint areas of metal on both sides of the
contact area, and they weld themselves together. These minute welded
particles then break away, and after the oil carries enough of them
off, the parts need replacement.
The role of liquid metals--usually molybdenum, tungsten, or zinc
compounds--is both to interfere with friction welding, and to
sacrifice itself to the wear that would otherwise devour engine
parts. Unfortunately, phosphorous compounds degrade catalytic
converter performance, so the feds limit the amount of additives like
zinc dialkyldithiophosphate in motor oils. But in nearly all
instances there is enough to last from one oil change to the next.
In the years before we had effective micron-level air and oil
filtering, abrasive engine wear was a problem. The typical spark-
ignition engine sucks in 10,000 gallons of air for every gallon of
fuel it consumes. If you don't filter that air, it carries grit into
your engine post-haste. The larger particles do little damage unless
they get caught between a valve and its seat, pitting both severely.
Virtually all dust particles are silica or silicon oxide, an
extraordinarily hard substance with plenty of sharp edges. Engines
with inadequate (or non-existent) air filters eat a huge amount of
this grit. The good news is, most of it leaves with the exhaust
gases. The bad news? What does stay can do severe damage, whether
its in the wrong place or carried around in the wrong oil.
Modern air and oil filters trap just about everything larger than a
micron (1/1,000,000th of a meter, or 0.000039 inch) in diameter. The
oil film separating an engine's moving parts envelops particles of
that size. Even very light oil provides this protection. SAE 5
seems watery, but it has a film depth of not less than 0.001 inch,
deep enough to submerge particles smaller than 26 microns.
Abrasive wear was a bigger problem back when the typical engine air
filter was a coarse screen capable of stopping nothing much smaller
than pea gravel. The old gravel strainers gave free passage to the
20-micron grit that does the worst damage, especially to piston rings.
Fine grit was/is still a great killer of roller cranks. Grit becomes
embedded in bearing cages and makes them depressingly effective
crankpin grinders. You can prevent this kind of damage by using the
thick oils, SAE 30 and above, envisioned and recommended by the
people who built these old engines.
Thick, high-viscosity oils are good for enveloping grit. They also
do a great job of sealing and cushioning, which are two important
functions of all motor oils (much more 30 years ago than today). The
aluminum piston alloys in use circa 1960 had high expansion rates and
poor high temperature strength. Accordingly, they needed to be
surrounded by thick oil, to seal the fire trying to blow past the
generous clearances--and to keep them from rattling in their bores.
Thick oils spread the concentrated loads between roller bearings and
their races. The mechanism of rolling-element bearing failure usually
is "brinelling," fatigue-related flaking, of the inner bearing race.
Under load, the race under the roller (or ball) yields minutely as
the bearing turns, just as a paved street yields to the weight of a
passing truck. And in time the bearing race, much like the street,
begins to break up.
Plain insert-type bearings can also fall victim to fatigue failure.
You can bring about their early demise by feeding them too-thick oil,
which will turn into too-thin oil in the bearing. The oil in plain
bearings, whether connecting rod inserts or the floating bushings in
a supercharger, is heated by fluid shearing. If the oil's viscosity
and bearing clearance are properly matched, there will be sufficient
oil flowing past the bearing to keep it cool.
When you pour SAE 40 into an engine designed for SAE 10-30, you may
intend to protect its bearings with the thicker oil. But the
increased oil viscosity, and resulting reduction of flow, can
overheat the bearing. The metals used in plain bearings--copper,
lead, and aluminum--typically lose half their ambient temperature
strength at 200 degrees F. Copper-lead bearings are stressed near
their elastic limit at redline crank speeds, even with crankcase oil
temperatures below 250 degrees F. Pour in some thick oil, or an
additive viscosity index improper, and you'll reduce the bearing's
oil flow, which will make it hotter and may cause it to fail.
Engine oils are viscosity-rated by subjecting them to the arcane arts
of a viscometer at 40 degrees F, then heating them and repeating the
test at 210 degrees F. When you see a 10W30 rating on an oil,
the "W" means the oil's base stock has actually been tested down to
zero degrees F with a cold cranking simulator. It is assumed, for
purposes of viscosity, that motor oils are "Newtonian" in that their
loss of viscosity with temperature (meaning that their rate of loss
is fairly constant.) The rate of loss is given as a viscosity index
number, and in this respect some oils are better than others.
Multi-grade oils are made so by chemical additives called "viscosity
index improvers." These additives contain either colloid ally
dispersed long-chain molecules that dissolve into true solution as
temperature rides, or spiral molecules that open up and get longer
with increases in temperature. Both of these actions "thicken" heat-
thinned oil. Add the right VI improver and you get, for example, an
oil that tests like SAE 10 at 40F, but looks more like SAE 30 at
210F. Multi-grade oil doesn't thicken with increased temperature; it
doesn't thin as much as single-grade oil.
One thing you should know about multi-grade oils is that their VI-
improving additives will wear out. You can fool mother nature, but
not forever: Long-chain molecules shear apart, so the 10-30 oil you
poured into your engine becomes 10-25 oil after a time, then 10-20,
10-25, right down to 10-10 if you cover enough hours between oil
changes.
Over the last couple of decades we have seen the rise of "synthetic"
and "synthetic blend" base stocks in motor oils. The big difference
between plain old refined oil and synthetic is the latter is, well,
synthesized. When crude oil is refined, it is effectively sifted.
The SAE 30 base stock you get in the sifting operation represents an
average of molecule sizes, some being larger and others smaller.
Shearing in a running engine breaks the big molecules apart faster
than the little ones, which reduces the average size of molecules in
the oil and thins it.
In contrast, synthetic base stocks' molecules are uniform in size,
having been assembled out of fragments in a molecular stew.
Synthetic oils also contain none of the waxes that can block low-
temperature flow, and none of the instant-sludge crude-oil cruds or
aromatics that vaporize and drift away the first time a spark plug
fires anywhere near them.
Some of the early synthetic motor oils were not impressive, which
were compounded using cheap glycols as a base. Union Carbide's
polyalkylenes oozed past gaskets and seals, some others synthesized
from gases returned to gaseous form in the hot engine environment.
The better synthetic base stocks in use today are record-holders on
the viscosity index scale. They still need a good squirt of VI
booster to qualify as multi-grade oils, but they need less of it than
refined base stocks. This is important, as polymeric viscosity index
improvers' long molecules are unstable in shear. The less help your
SAE 10W30 motor oil needs to meet its high temperature obligations,
the longer it will be effective.
Good synthetic motor oils also have better non-Newtonian, "apparent
viscosity" behaviors. Oil displaying these "kinematically
diminished" properties behaves like thinner oil when rubbing speeds
are high enough to build a thick fluid wedge.
Which synthetic oils are best in terms of apparent viscosity? I
don't know, and neither does anyone who lacks a laboratory full of
expensive, complicated equipment. I also don't know which additives,
or how much of each, is present in the containers of motor oil--
refined or synthetic--you'll see displayed at dealerships, service
stations, and the like. That information is a closely held trade
secret.
So after all this talk of motor oils, how do you tell good from bad?
The bottom line here is, you buy the label on the container; you buy
reputation. When you see a plastic bottle labeled "zowie lube," with
small print that says it was packaged by "O'grady's Motor and
Hemorrhoid products," put it back on the shelf and reach for
something familiar. When I tell you to buy name-brand products, I'm
not just sucking up to anybody's oil.
Castrol is not the only oil out there, but I will tell you the
company has been making motor oils since we've had motors and I don't
think it would knowingly sell you anything that would tarnish it's
good name. I've used Castrol's motor oils for both racing and street
applications, without disappointment. Refined-based GTX, sold super-
cheap at supermarkets everywhere, is very good motor oil and may be
better than some higher-priced synthetics.
Mobil, long ago began developing synthetic motor oils and put its
considerable technical resources to work creating a good one. They
came up with Mobil 1, oil using mostly polyalphaolefin base stock
reinforced with a big percentage of polyol ester, the latter being an
especially good lubricant in its own right. Mobil 1 probably is
today's best widely available motor oil. I bought (yes, bought!)
Mobil 1 for use in my own vehicles
Red Line is making a name for itself as a source of all-synthetic
motor oils, and this company, like Mobil, relies on big percentages
of polyol esters in its base stocks. My contacts in two- and four-
wheeled racing tell me Red Line's oils are producing excellent
results in everything from NASCAR's stockers to motorcycle GP
racing's shrieking 2-stroke engines.
Keep in mind that your engine was extensively tested with its
cavities full of the lubricants specified by its maker. All auto
manufacturers don't test their models on oil specially compounded to
keep engines, clutches, and transmissions happy, they instead do the
sensible thing and design hardware compatible with the oils they know
you'll be able to find. It's the smart thing to do, and it works
right up to the point where you ignore their advice.
From: monte350v8 [mailto:mewood@eastex.net]
Sent: Sunday, March 16, 2003 12:32 PM
Subject: [Kohler and Onan Engine Club] The FACTS are against using MoS2 (Moly)
Molybdenum Disulfide as a solid Lubricant
The following is taken verbatim from The CRC Handbook of Lubrication
(Tribology), by E. Richard Booser, sponsored by the Society of
Tribologists and Lubrication Engineers, Copyright, 8th printing, 1992.
Vol. II, page 286, Dispersion in Oils and Greases.
"Automotive experience has confirmed the beneficial effects of
Molybdenum disulfide additions to oils in reducing both wear and fuel
consumption (friction). Two cautionary comments are in order. First,
detergent additives in automotive oils can inhibit the wear reducing
ability of the MoS2 and graphite, and some anti-wear additives can
even increase wear rates slightly. Second, solid lubricant additions
can affect the oxidation stability of oils and greases, and this may
influence the concentration of oxidation inhibitors required; smaller
particles have a greater effect on oxidation stability than larger
ones."
Vol II, page 272, Lamellar Solids.
" MoS2 has a lamellar structure, but with inter-lamellar bonding
between two adjacent layers of Sulfur atoms. The bonding is
relatively weak, via Van der Waals forces only, and MoS2 is therefore
an intrinsic solid lubricant. Absorbed vapors usually increase
friction but the effects are comparatively small. The thermal
stability of MoS2 in non-oxidizing environments is of the order of
1100 deg C., but in air oxidation begins to become significant at
around 350 to 400 deg C. The normal air oxidation product is MoO3,
once believed to be abrasive but now known to be virtually innocuous.
A major concern of MoS2 is the presence of abrasive impurities. The
reasons for concern are twofold. First and foremost, chemical
analyses provide no information about the form of impurity; abrasion
by hard particles such as SiO2, depends greatly on their shape and
size. Second, other factors in addition to impurities can play a role
in abrasiveness, e.g. crystallite modifications or anisotropy in
hardness."
From NASA Technical Memorandum 104525, Tribology Needs For Future
Space and Aeronautical Systems, Robt. L. Fusaro, Lewis Research
Center, Cleveland OH, Dec. 1991 - Page 9, Solid Lubricant Factors.
"Most solid lubricant films do not function well in a liquid
environment, whether it be water or oil. Even the miniscule amount of
oil deposited by an inquiring finger can drastically affect
tribological properties and reduce endurance life. A small hard
particle can imbed itself in a film and severely abrade the counter-
face."
It is also a fact that there are no Mil-Spec Oil Dispersions in
existence that include MoS2. There are paste and grease Mil-Spec
Dispersions however, that do contain MoS2.
The greatest problems associated with oil dispersions is the
alteration of viscosity by the addition of solids which causes a
shearing of the fluid film and an increase in traction under
Hydrodynamic and Elastohydrodynamic regimes. This can and often does
produce a consumption of more energy in the system and works in
opposition to energy efficient systems.
The basic message is change your oil often with a high quality product that meets the engine manufacturer's recommended rating.
This excerpt is from a small engine forum:
--------------------------------------------------------------------------------------
From: monte350v8 [mailto:mewood@eastex.net]
Sent: Sunday, March 16, 2003 10:22 AM
Subject: [Kohler and Onan Engine Club] Motor Oil 101
Motor Oil: The myths, facts, and mysteries of the slippery stuff that keeps your engine happy.
Here's the bottom line when it comes to motor oils: you really can't
go wrong by following the recommendations given in your owner's
manual. Your engine's maker has dyno-tested its engine with a
crankcase full of the specified oil, or one with the same American
Petroleum Institute (API) rating. You can be sure that particular
oil will do the job. Will it do the job better than any other oil?
Will it do the job if the engine is no longer as its manufacturer
made it? Not necessarily, as you will learn by reading further.
The API's ratings once went from 'SA' (guaranteed to be oil) through
the alphabet to 'SE' and was extended to 'SE/CC' (you cant drive a
nail through a film of this stuff.) Today the API has fewer
performance grades, only 'SH' and 'SG' for spark-ignition engines,
with an 'SH/CD' rating for oils good enough to be used in passenger-
car diesels. The motor oils bearing these API markings have been
test-certified for today's engines, which are in turn constructed
with these oils in mind.
You should be aware that motor oils are now being compounded not just
for lubrication, but to improve fuel economy as well. Oils have
always been compounded with a thought for fluid drag; this is the
first time its been made a priority. The API has two economy
ratings: "energy conserving" for motor oils that yield a 1.5%
reduction in fuel consumption as compared with a reference
oil; "energy conserving II" is an oil that provides a 2.7% drop in
fuel consumption.
As you might expect, energy-conserving oils drag reduction benefits
also show up as increased horsepower. Both thermal and mechanical
losses diminish the power liberated in the combustion process on its
way to the output shaft. The work of pumping air in and out of the
engine accounts for the majority of the mechanical losses. The rest
is mostly lost to fluid drag on the piston, which is, all other
things being equal, largely a function of oil viscosity.
Friction exists even in the absence of actual contact between opposed
surfaces. The cylinder wall's oil film normally prevents it from
being touched by the piston; it is a source of friction itself, if we
take that to mean a resistance to relative motion. Millions of
molecules on each side of the gap try to stick together and get
pulled apart. The sum of millions of molecule's minute resistance to
separation comprises viscous drag, the source of most friction in a
running engine.
Viscosity aside, the most important property of oil is that it
be "oily." Introducing any liquid between a piston and cylinder
wall, for example, will reduce friction between the two surfaces.
The degree to which friction will be reduced is, broadly speaking, a
function of the liquid's viscosity. But maple syrup and motor oil of
essentially identical viscosity do not lubricate equally, as you
discover by rubbing samples of each between thumb and forefinger.
If "oiliness" were the only quality to be considered in choosing
motor oils, we'd be squeezing all ours from castor beans. Castor
oil, the smell of which once perfumed the air at motor races, is the
oiliest of oils and it remains in some respects the supreme
lubricant. It does oxidize too readily, however, forming ring-
sticking gums and varnishes, and daubing fouling deposits on spark
plugs. In a running engine, castor oil goes right to work gluing
piston rings in their grooves and slathering gum and varnish
everywhere. You wouldn't want it in any engine that can survive
without its help.
But castor oil, a mixture of ricinoleic and triricinoleic glycerides,
plus 10-12% of other fatty acids, remains one of the best lubricants
for 2-stroke racing engines. Castor oil clings to metal with such
tenacity it cannot be removed except by machining. It is an
exceptionally effective film lubricant.
Oil forming a hydrodynamic wedge between surfaces keeps pistons and
bushing-type bearings from metal-to-metal contact. Viscosity pulls
the oil between a moving piston and its adjacent cylinder wall, or a
shaft and a bearing, and pressurizes the gap. The pressure increases
with viscosity and speed, and a well-designed engine almost totally
prevents scrubbing contact.
The qualifying "almost" is needed because hydrodynamic action is not
present in an engine at start-up, and it collapses around the pistons
and rings at the end of their strokes. Under these conditions, parts
are protected only by film lubrication, which is provided by the
bipolarity of the oil molecules. The molecules behave like tiny
magnets and adhere to ferrous metals and each other.
One of the great improvements in motor oils came circa 1950, when the
detergent/dispersant additives developed for diesels came into more
general use. Alas these brought with them unfortunate consequences
for old, high-mileage engines. In those, the detergents sometimes
dislodged great clots of oxidized oil filth to clog filters and oil
passages. Engine failures caused by detritus liberated in this
manner put additive oils in bad repute, with the results that some
people still buy and use straight non-additive oils.
The first oil additive was probably the spoonful of sulfur old-time
truck operators tossed into axle and transmission housings. The
sulfur reacted with gear-tooth steel to give the gears an iron
sulfide film. The film was important because the relative speeds
between meshing gears is too low to form a fluid wedge strong enough
to resist the extremely high gear-tooth loads.
Engines also have points at which loadings can exceed the carrying
capacity of the fluid wedge. Take the tiny contact area between the
exhaust cam and follower, for example. The load there rises to
roughly 1500 pounds for every ounce of valve train weight at high
engine speeds. Full throttle adds 80 pounds of load for every square
inch of valve head area, meaning the load focused on the cam/follower
can reach pressures in the order of 20,000 pounds per square inch.
Cams would have to spin much faster than they do (half crank speed)
to work up a fluid wedge capable of carrying such high loadings. So
the job has to be done with film lubrication, which means more
viscous oil, one with special properties (castor) or an extreme
pressure (EP) additive. It's obvious that film lubrication is
important, where some of us go wrong is in leaping to the conclusion
that those who compound motor oils have overlooked this very point.
Most parts dealer's shelves usually have a selection of additive
liquids that claim to be a supreme cure all oil additive. This stuff
reduces the friction in your wallet enough to make money slip out of
it, but may not do anything else. About the best you can hope from
additives is that it will either be more of the same additives
already in good-quality motor oils, or at least not get in the way of
the additives that can do something useful.
Film-condition additives usually are chemically and/or thermally
reactive. The sulfur- and phosphorus-based compounds react with iron
to form slippery iron sulfides, as previously noted, or wear-
resistant iron phosphates. Fatty acids, like those in castor oils,
react with iron to make low-friction iron soaps.
Thermally reactive "liquid metals" like molybdenum dithiophospate,
are oil-soluble chemical compounds; molybdenum sulfide, on the other
hand, is a cheap dry-slide lubricant sometimes used in greases. If
you put MOS or other dry-slide lubricant powders like colloidal
graphite in motor oil, these solids may settle or filter out. Worse,
they may become a barrier blocking the more effective reactive
additives.
The liquid metals dissolve in oil, like salt in water, and remain in
solution at all normal engine-operating temperatures. But when
friction heats the liquid metal compounds they come apart and their
metallic component is plated on the hot spot. This stops the most
potent, least obvious wear process in today's filter-protected
engines: direct, scrubbing contact between a cam and follower, gear
teeth, etc. This contact results in wear largely due to friction
welding: Friction melts pinpoint areas of metal on both sides of the
contact area, and they weld themselves together. These minute welded
particles then break away, and after the oil carries enough of them
off, the parts need replacement.
The role of liquid metals--usually molybdenum, tungsten, or zinc
compounds--is both to interfere with friction welding, and to
sacrifice itself to the wear that would otherwise devour engine
parts. Unfortunately, phosphorous compounds degrade catalytic
converter performance, so the feds limit the amount of additives like
zinc dialkyldithiophosphate in motor oils. But in nearly all
instances there is enough to last from one oil change to the next.
In the years before we had effective micron-level air and oil
filtering, abrasive engine wear was a problem. The typical spark-
ignition engine sucks in 10,000 gallons of air for every gallon of
fuel it consumes. If you don't filter that air, it carries grit into
your engine post-haste. The larger particles do little damage unless
they get caught between a valve and its seat, pitting both severely.
Virtually all dust particles are silica or silicon oxide, an
extraordinarily hard substance with plenty of sharp edges. Engines
with inadequate (or non-existent) air filters eat a huge amount of
this grit. The good news is, most of it leaves with the exhaust
gases. The bad news? What does stay can do severe damage, whether
its in the wrong place or carried around in the wrong oil.
Modern air and oil filters trap just about everything larger than a
micron (1/1,000,000th of a meter, or 0.000039 inch) in diameter. The
oil film separating an engine's moving parts envelops particles of
that size. Even very light oil provides this protection. SAE 5
seems watery, but it has a film depth of not less than 0.001 inch,
deep enough to submerge particles smaller than 26 microns.
Abrasive wear was a bigger problem back when the typical engine air
filter was a coarse screen capable of stopping nothing much smaller
than pea gravel. The old gravel strainers gave free passage to the
20-micron grit that does the worst damage, especially to piston rings.
Fine grit was/is still a great killer of roller cranks. Grit becomes
embedded in bearing cages and makes them depressingly effective
crankpin grinders. You can prevent this kind of damage by using the
thick oils, SAE 30 and above, envisioned and recommended by the
people who built these old engines.
Thick, high-viscosity oils are good for enveloping grit. They also
do a great job of sealing and cushioning, which are two important
functions of all motor oils (much more 30 years ago than today). The
aluminum piston alloys in use circa 1960 had high expansion rates and
poor high temperature strength. Accordingly, they needed to be
surrounded by thick oil, to seal the fire trying to blow past the
generous clearances--and to keep them from rattling in their bores.
Thick oils spread the concentrated loads between roller bearings and
their races. The mechanism of rolling-element bearing failure usually
is "brinelling," fatigue-related flaking, of the inner bearing race.
Under load, the race under the roller (or ball) yields minutely as
the bearing turns, just as a paved street yields to the weight of a
passing truck. And in time the bearing race, much like the street,
begins to break up.
Plain insert-type bearings can also fall victim to fatigue failure.
You can bring about their early demise by feeding them too-thick oil,
which will turn into too-thin oil in the bearing. The oil in plain
bearings, whether connecting rod inserts or the floating bushings in
a supercharger, is heated by fluid shearing. If the oil's viscosity
and bearing clearance are properly matched, there will be sufficient
oil flowing past the bearing to keep it cool.
When you pour SAE 40 into an engine designed for SAE 10-30, you may
intend to protect its bearings with the thicker oil. But the
increased oil viscosity, and resulting reduction of flow, can
overheat the bearing. The metals used in plain bearings--copper,
lead, and aluminum--typically lose half their ambient temperature
strength at 200 degrees F. Copper-lead bearings are stressed near
their elastic limit at redline crank speeds, even with crankcase oil
temperatures below 250 degrees F. Pour in some thick oil, or an
additive viscosity index improper, and you'll reduce the bearing's
oil flow, which will make it hotter and may cause it to fail.
Engine oils are viscosity-rated by subjecting them to the arcane arts
of a viscometer at 40 degrees F, then heating them and repeating the
test at 210 degrees F. When you see a 10W30 rating on an oil,
the "W" means the oil's base stock has actually been tested down to
zero degrees F with a cold cranking simulator. It is assumed, for
purposes of viscosity, that motor oils are "Newtonian" in that their
loss of viscosity with temperature (meaning that their rate of loss
is fairly constant.) The rate of loss is given as a viscosity index
number, and in this respect some oils are better than others.
Multi-grade oils are made so by chemical additives called "viscosity
index improvers." These additives contain either colloid ally
dispersed long-chain molecules that dissolve into true solution as
temperature rides, or spiral molecules that open up and get longer
with increases in temperature. Both of these actions "thicken" heat-
thinned oil. Add the right VI improver and you get, for example, an
oil that tests like SAE 10 at 40F, but looks more like SAE 30 at
210F. Multi-grade oil doesn't thicken with increased temperature; it
doesn't thin as much as single-grade oil.
One thing you should know about multi-grade oils is that their VI-
improving additives will wear out. You can fool mother nature, but
not forever: Long-chain molecules shear apart, so the 10-30 oil you
poured into your engine becomes 10-25 oil after a time, then 10-20,
10-25, right down to 10-10 if you cover enough hours between oil
changes.
Over the last couple of decades we have seen the rise of "synthetic"
and "synthetic blend" base stocks in motor oils. The big difference
between plain old refined oil and synthetic is the latter is, well,
synthesized. When crude oil is refined, it is effectively sifted.
The SAE 30 base stock you get in the sifting operation represents an
average of molecule sizes, some being larger and others smaller.
Shearing in a running engine breaks the big molecules apart faster
than the little ones, which reduces the average size of molecules in
the oil and thins it.
In contrast, synthetic base stocks' molecules are uniform in size,
having been assembled out of fragments in a molecular stew.
Synthetic oils also contain none of the waxes that can block low-
temperature flow, and none of the instant-sludge crude-oil cruds or
aromatics that vaporize and drift away the first time a spark plug
fires anywhere near them.
Some of the early synthetic motor oils were not impressive, which
were compounded using cheap glycols as a base. Union Carbide's
polyalkylenes oozed past gaskets and seals, some others synthesized
from gases returned to gaseous form in the hot engine environment.
The better synthetic base stocks in use today are record-holders on
the viscosity index scale. They still need a good squirt of VI
booster to qualify as multi-grade oils, but they need less of it than
refined base stocks. This is important, as polymeric viscosity index
improvers' long molecules are unstable in shear. The less help your
SAE 10W30 motor oil needs to meet its high temperature obligations,
the longer it will be effective.
Good synthetic motor oils also have better non-Newtonian, "apparent
viscosity" behaviors. Oil displaying these "kinematically
diminished" properties behaves like thinner oil when rubbing speeds
are high enough to build a thick fluid wedge.
Which synthetic oils are best in terms of apparent viscosity? I
don't know, and neither does anyone who lacks a laboratory full of
expensive, complicated equipment. I also don't know which additives,
or how much of each, is present in the containers of motor oil--
refined or synthetic--you'll see displayed at dealerships, service
stations, and the like. That information is a closely held trade
secret.
So after all this talk of motor oils, how do you tell good from bad?
The bottom line here is, you buy the label on the container; you buy
reputation. When you see a plastic bottle labeled "zowie lube," with
small print that says it was packaged by "O'grady's Motor and
Hemorrhoid products," put it back on the shelf and reach for
something familiar. When I tell you to buy name-brand products, I'm
not just sucking up to anybody's oil.
Castrol is not the only oil out there, but I will tell you the
company has been making motor oils since we've had motors and I don't
think it would knowingly sell you anything that would tarnish it's
good name. I've used Castrol's motor oils for both racing and street
applications, without disappointment. Refined-based GTX, sold super-
cheap at supermarkets everywhere, is very good motor oil and may be
better than some higher-priced synthetics.
Mobil, long ago began developing synthetic motor oils and put its
considerable technical resources to work creating a good one. They
came up with Mobil 1, oil using mostly polyalphaolefin base stock
reinforced with a big percentage of polyol ester, the latter being an
especially good lubricant in its own right. Mobil 1 probably is
today's best widely available motor oil. I bought (yes, bought!)
Mobil 1 for use in my own vehicles
Red Line is making a name for itself as a source of all-synthetic
motor oils, and this company, like Mobil, relies on big percentages
of polyol esters in its base stocks. My contacts in two- and four-
wheeled racing tell me Red Line's oils are producing excellent
results in everything from NASCAR's stockers to motorcycle GP
racing's shrieking 2-stroke engines.
Keep in mind that your engine was extensively tested with its
cavities full of the lubricants specified by its maker. All auto
manufacturers don't test their models on oil specially compounded to
keep engines, clutches, and transmissions happy, they instead do the
sensible thing and design hardware compatible with the oils they know
you'll be able to find. It's the smart thing to do, and it works
right up to the point where you ignore their advice.
From: monte350v8 [mailto:mewood@eastex.net]
Sent: Sunday, March 16, 2003 12:32 PM
Subject: [Kohler and Onan Engine Club] The FACTS are against using MoS2 (Moly)
Molybdenum Disulfide as a solid Lubricant
The following is taken verbatim from The CRC Handbook of Lubrication
(Tribology), by E. Richard Booser, sponsored by the Society of
Tribologists and Lubrication Engineers, Copyright, 8th printing, 1992.
Vol. II, page 286, Dispersion in Oils and Greases.
"Automotive experience has confirmed the beneficial effects of
Molybdenum disulfide additions to oils in reducing both wear and fuel
consumption (friction). Two cautionary comments are in order. First,
detergent additives in automotive oils can inhibit the wear reducing
ability of the MoS2 and graphite, and some anti-wear additives can
even increase wear rates slightly. Second, solid lubricant additions
can affect the oxidation stability of oils and greases, and this may
influence the concentration of oxidation inhibitors required; smaller
particles have a greater effect on oxidation stability than larger
ones."
Vol II, page 272, Lamellar Solids.
" MoS2 has a lamellar structure, but with inter-lamellar bonding
between two adjacent layers of Sulfur atoms. The bonding is
relatively weak, via Van der Waals forces only, and MoS2 is therefore
an intrinsic solid lubricant. Absorbed vapors usually increase
friction but the effects are comparatively small. The thermal
stability of MoS2 in non-oxidizing environments is of the order of
1100 deg C., but in air oxidation begins to become significant at
around 350 to 400 deg C. The normal air oxidation product is MoO3,
once believed to be abrasive but now known to be virtually innocuous.
A major concern of MoS2 is the presence of abrasive impurities. The
reasons for concern are twofold. First and foremost, chemical
analyses provide no information about the form of impurity; abrasion
by hard particles such as SiO2, depends greatly on their shape and
size. Second, other factors in addition to impurities can play a role
in abrasiveness, e.g. crystallite modifications or anisotropy in
hardness."
From NASA Technical Memorandum 104525, Tribology Needs For Future
Space and Aeronautical Systems, Robt. L. Fusaro, Lewis Research
Center, Cleveland OH, Dec. 1991 - Page 9, Solid Lubricant Factors.
"Most solid lubricant films do not function well in a liquid
environment, whether it be water or oil. Even the miniscule amount of
oil deposited by an inquiring finger can drastically affect
tribological properties and reduce endurance life. A small hard
particle can imbed itself in a film and severely abrade the counter-
face."
It is also a fact that there are no Mil-Spec Oil Dispersions in
existence that include MoS2. There are paste and grease Mil-Spec
Dispersions however, that do contain MoS2.
The greatest problems associated with oil dispersions is the
alteration of viscosity by the addition of solids which causes a
shearing of the fluid film and an increase in traction under
Hydrodynamic and Elastohydrodynamic regimes. This can and often does
produce a consumption of more energy in the system and works in
opposition to energy efficient systems.
4Fighter
TY 4 Stroke God
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And that's why I continue to use Yamalube and follow the recommended maintenance procedures. Yamaha, or my dealer will never be able to say that my engine failure was caused by using the wrong oil/filter. Now, it would be different if I had to send away for the stuff, or drive a long distance to get it, but since it's readily available, and what the OEM says to use, I use it.
