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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.
AUTOMOTIVE 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
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 enginešs 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, cavitation
and mechanical failure.
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 drivetrain 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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