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The
True Measure of Lubricant Quality
By Ed Newman
This article appeared in Power
Stroke Registry, Summer Edition 2003
Making and recording measurements has been one of the hallmarks of the Age of
Enlightenment. It seems like modern people measure everything. We have measures
of time, such as weeks, hours, minutes, and years. We have measures of mass,
such as grams, pounds and tons. We have measures of sound volume, of energy, of
radioactivity, of pressure, of type font sizes, of land mass, and of speed.
AUTOMOTOTIVE RELATED MEASUREMENTS
Horsepower, as you might guess, is the amount of power exerted by one horse
pulling. After many careful measurements James Watt, inventor of the steam
engine, determined that a horse can lift 550 pounds at a rate of one foot per
second, which translates into 745.7 watts. Some clever American engineers
decided that manpower should have a measurement as well, equivalent to 0.1
horsepower or 74.57 watts.
MPG is the familiar acronym for miles per gallon, which measures the rate of
fuel consumption in a motor vehicle. One mile per gallon equals approximately
0.4252 kilometers per liter. MPH is our common measure of speed. One mile per
hour equals 22/15ths feet per second or 1.609 kilometers per hour or 0.447
meters per second.
RPM means revolutions per minute, a unit of frequency as a measure of
rotation rates in mechanics. In cars RPM is measured by a tachometer. Some
motorists pay attention to RPM so they don't over rev and cause component
failure. Race car drivers try to keep RPM rates in a range that will provide
maximum power.
OIL MEASURES
A quart as a unit of volume is so named because it represents one quarter of
a gallon. When measuring liquid, one quart is 32 fluid ounces, or 57.75 cubic
inches. On the other hand, when measuring dry goods like pecans or blueberries,
a quart is 67.201 cubic inches. Go figure.
Drums are sometimes used for measuring oil, containing 55 U.S. gallons or
about 208.198 liters. Drums are not the same as barrels, the standard unit of
volume for measuring crude. One drum is equivalent to 1.3095 barrels. A barrel
is equivalent to 42 U.S. gallons, which is coincidentally the same size as a
traditional wine barrel, more commonly called a tierce.
But what about oil quality? What are the criteria that are important when
measuring the performance quality of a motor oil?
Part of the answer comes from understanding the role that motor oils play
when it comes to engine lubrication. Another part of the answer comes from
understanding that we live in a scientific age in which nearly everything can
be, and often has been, measured. Knowing what to measure and how to measure it
is an important part of good decision making. We're talking motor oil here.
THE ROLE OF MOTOR OIL
Before we can discuss what makes a good motor oil, it helps to understand
what role motor oil actually plays in the performance of an engine.
While motor oils serve a variety of functions, they are primarily necessary
to lubricate and to cool the engine. When the engine is at rest, the motor oil
sits in the bottom of the engine block in what is called the oil pan. Upon
start-up, an oil pump feeds oil from the pan to the oil distribution system by
means of a network of passages, tubes, grooves and holes leading to the engine
bearings and other surfaces needing pressurized oil for lubrication. Other
parts, like the overhead valve system, receive a carefully controlled quantity
of non-pressurized oil through splashing or spray.
In addition to lubricating and cooling engine parts, motor oil must allow easy
starting, protect the engine from corrosion and oxidation, keep the engine
clean, form a tight seal between piston rings and cylinder walls and help the
engine use fuel efficiently.
In days gone by motor oil was made from the throwaway byproducts of a barrel
of crude oil after everything useful was taken from it. In those early days the
filter, if you had one at all, was a by-pass type, filtering only a small
percentage of the oil. In some instance the filter was little more than a
screen and the oil was changed every five hundred or thousand miles. (Some of us
recall grandpa's stories of tires needing to be changed on every trip to town,
the idea of longevity being somewhat foreign back then.)
As cars and their engines became more sophisticated, so too the requirements
of a lubricant became increasingly demanding. In the 1960's jet fighter pilots
and their mechanics were becoming aware of the advantages of synthetic oils, and
a few of them experimented with the notion of synthetic lubrication for
automobiles. One of these pilots, Lt. Colonel Albert J. Amatuzio, went further
than the haphazard experiments of his peers. His ten year quest resulted in the
development of AMSOIL, the first automotive synthetic motor oil to exceed the
certification requirements of the American Petroleum Institute (API).
SYNTHETIC VS. CONVENTIONAL PETROLEUM
Conventional lubricants are refined from crude oil which has thousands of
types of molecules. Refining is a process of physically separating the
impurities from the oil and further separating the light and heavy components.
Because refining separates products by weight, it groups molecules of similar
weight and dissimilar structure. The result is a lubricant with a wide
assortment of molecules. Some of the substances in crude oil are detrimental to
lubrication. Paraffins, for example, are a common conventional oil contaminant
(wax) that causes motor oil to thicken in cold temperatures.
Synthetic motor oils are made from pure chemicals, not refined crude. Their
components are chemically reacted to produce finished products with pre-designed
performance characteristics. Because of their molecular uniformity, they excel
in reducing friction, which improves fuel efficiency, controls heat and reduces
wear. This molecular uniformity also helps synthetics resist thinning in hot
temperatures and thickening in cold.
MEASURES THAT MATTER
The American Society for Testing and Materials recognized the need for
uniform procedures that can be duplicated and verified by laboratories in any
location. The goal of establishing standards is so important that the official
publication of ASTM International is called Standardization News.
Founded in 1898 and completely voluntary, ASTM is now one of the largest
non-profit standards development systems in the world. The organization
currently has 134 committees that write standardized test methods for materials,
products, systems and services. More than 8500 ASTM specifications have been
established for products as diverse as metal, paints, plastics, textiles,
energy, consumer products, medical services and instruments and even the
environment.
Developing standard measurement methods is part of the task of ASTM. Equally
important is determining what measures are important, tests that actually
correspond to what the function of motor oil is intended to fulfill. What
follows here are some tests commonly used to evaluate motor oil performance.
ASTM D-445 Kinematic Viscosity
The proper operation of equipment depends on the proper kinematic viscosity of
the oil at operating temperatures. Kinematic viscosity is a measure of a
liquid's flow under the influence of gravity. Some companies formulate their
lubes to tighter specs than others. One recent study revealed that one in five
off-the-shelf motor oils tested were outside the acceptable performance range
for their stated viscosities.
ASTM D-2270 Viscosity Index
This test indicates how much a lube's viscosity will change according to changes
in temperature from 40 degrees C and 100 degrees C. The higher the viscosity
index the better for motor oils that must perform in locations with temperature
variations.
ASTM D-5293 Cold Crank Simulator Apparent Viscosity
Cold crank viscosity affects the startability of engines in cold temperatures.
Low cold cranking viscosities make for easier cold cranking and more dependable
cold temperature starting, and less drain on batteries.
ASTM D-3829 Borderline Pumping Temperature
This test is used to predict the lowest temperature at which a motor oil can be
continuously and adequately supplied to an engine¹s components. As the name
suggests, the lower the temperature, the better the oil circulates in cold
weather. Synthetic oils are famed for the extreme low temperature protection.
ASTM D-97 Pour Point
This test identifies the lowest temperature at which oil flows.
ASTM D-92 Flash Point and Fire Point
Flash point indicates the temperature at which a specimen vapors will ignite.
Flash point assesses the overall hazard of a material and is used in shipping
and safety regulations to define "flammable" and "combustible" materials. Fire
point measures the temperature at which a specimen will remain burning for five
seconds. Synthetic lubricants with high flash and fire points are safer to use
and transport than petroleum lubes with lower ones. High flash point is
indicative of a greater high temperature operating range and better quality base
stock.
ASTM D-4683 High Temp, High Shear Viscosity
This test is representative of the conditions encountered in the bearings of
automotive engines in severe service. Lubricants with high scores, such as
premium synthetics, maintain their viscosity in high temperatures after exposure
to high shear. This means that they continue to protect bearings even after
exposure to severe service conditions.
ASTM D-892 Foaming Tendency
This test is important because of the turbulent environment in which motor oils
are required to perform. Foaming can lead to inadequate lubrication,
cavitations and mechanical failure.
(Foam is a mixture of oil and air, and the last time I checked, air was not a
lubricant ! )
ASTM D-4172B Four Ball Wear Test
The Four Ball Wear Test determines the relative wear prevention properties of
lubricants in sliding contact. The test involves three fixed balls in a bath of
lubricant with a fourth ball in rolling contact under pressure at a specific
level of severity. Wear protection is gauged by measuring the wear scar that
develops. A smaller wear scar means better protection in typical engine
operations.
ASTM D-5800 Noack Volatility
Oil volatility is the measure of how susceptible oil is to boil-off under high
heat conditions. Petroleum oils experience significant boil-off during high
temperature engine operation and subsequently higher oil consumption.
Evaporation loss contributes to damaging deposits, sticky piston rings and oil
blow-by, resulting in a drag on performance and reduced engine life. Synthetic
oils are far more impervious to this kind of degradation. The lower volatility
of synthetics is another reason they are also better for the environment than
conventional products.
SAE J1321 Joint TMC/SAE Fuel Consumption Test Procedure - Type II
The Society of Automotive Engineers has devised a test to measure fuel
consumption and fuel economy. In a demonstration involving over-the-road trucks
an improvement of 8.2% was achieved by switching from conventional lubes to
synthetic lubricants (in this case AMSOIL products) in the drive train and
engine.
Here's an interesting, undisputed fact. By every one of these measures premium
synthetic motor oils are superior to conventional petroleum motor oils. This
truth is never even questioned by industry professionals.
So why, one might ask, isn't everyone using synthetic motor oils and lubes?
Here's one possible reason. To divert attention away from the performance
measures above the major oil companies focus on one other measure: ….. price.
PRICE
Ironically, we live in an era in which people are spending more money than ever
on large vehicles or cool looking vehicles -- PT Cruisers, SUVs, Hummers, and
dualies. Insurance payments alone in most households run ten times greater than
motor oil costs. People are passionate about their vehicles. How can they not
be equally dedicated to protecting their investment by using premium lubricants
that promise longer life to the object of their passion. You wouldn't expect
price to be that big of a deal, yet it is for some people. For this reason the
price myth must be addressed.
When people talk about price, they generally think in terms of initial cost
instead of life cycle cost. Price is only an issue if you apply the 3,000 mile
oil change rule to all motor oils alike. In truth, the service life of
synthetics can be extended much longer due to their resistance to oxidation and
other forms of degradation. With proper filtration engine oil can be safely
used for much longer periods, and is thereby less costly than petroleum in the
long run. Add to this the reduced fuel consumption, fewer maintenance bills and
optimal performance characteristics and running anything but a premium synthetic
motor oil should not even be a consideration.
CLOSING THOUGHTS
As you can readily see there is no single measure that stands alone as the
signature of superior performance. A motor oil serves a variety of functions in
a range of roles inside the engine. What tests do show is that synthetic motor
oils as a class are far and away superior to petroleum based products.
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