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Synthetic Lubricants
Tom Schaefer
Hatco
Corporation
For most products, the word "Synthetic" is often
a negative term, implying cheap, imitation, or artificial
- just not up to the "real thing". In the world
of lubrication, however, just the opposite is true. Synthetic
lubricants by virtually all measures are distinctly superior
to their petroleum counterparts, and distinctly more expensive.
In this market, Synthetic clearly means Premium.
Defining the term "synthetic lubricant" is becoming
more controversial these days, but in general it refers to
a lubricant or grease whose basestock has been manufactured
by chemical synthesis or organic reaction, as opposed to being
extracted or refined from naturally occurring oils. In many
respects synthetics represent a different approach altogether
from conventional petroleum based oils in that their molecular
structures are custom designed and tailored to meet specific
performance targets. To appreciate this concept better we
need to understand something about the composition of lubricants
and how they work.
Most lubricants consist of a basestock and various additives
selected to improve or supplement the basestock's performance.
The basestock is the primary component, usually 70 to 99%
of the finished oil or grease, and its properties play a vital
role. To a great degree the structure and stability of the
basestock dictate the flow characteristics of the oil and
the temperature range in which it can operate, as well as
many other vital properties such as volatility, lubricity,
and cleanliness. Additives enhance these properties or impart
new ones, such as improving stability at both high and low
temperatures, modifying the flow properties, and reducing
wear, friction, rust and corrosion. The basestocks and additives
work together and must be carefully selected and balanced
to allow the finished oil to do its intended job, which includes
protecting moving parts from wear, removing heat and dirt,
preventing rust and corrosion, and improving energy efficiency.
Since the basestock is the dominate component with the most
important role, one obvious way to make a better oil is to
start with a better basestock. That is exactly what synthetic
oils endeavor to accomplish.
Conventional petroleum basestocks or mineral oils begin with
crude oil, a mixture of literally hundreds of different molecules
derived from the decomposition of prehistoric plant and animal
life. The lighter more volatile components of crude oil are
stripped away to make gasoline and other fuels, and the heaviest
components are used in asphalt and tar. It's the middle cuts
that have the right thickness or viscosity for lubricants,
but first they must be cleaned up; undesirable components
such as waxes, unsaturated hydrocarbons, and nitrogen and
sulfur compounds must be removed. Modern processing techniques
do a pretty good job of removing these undesirable components,
good enough for well over 95% of the world's lubricant applications,
but they cannot remove all of the bad actors. And it's these
residual "weak links" that limit the capabilities
of mineral oils, usually by triggering breakdown reactions
at high temperatures or freezing up when cold. These inherent
weaknesses limit the temperature range in which mineral oils
can be used and shorten the useful life of the finished lubricant.
Synthetic basestocks, on the other hand, start from relatively
pure and simple chemical building blocks which are then reacted
together or synthesized into new, larger molecules. The resulting
synthetic basestock consists only of the pre-selected molecules
and has no undesirable weak links that inhibit performance.
This ability to pre-select or design specific ideal molecules
tailored for a given job, and then create those molecules
and only those molecules, opens a whole new world for making
superior basestocks for lubricants. If fact the entire formulation
approach is different: instead of trying to clean up a naturally
occurring chemical soup to acceptable levels with a constant
eye on cost, the synthetic molecular engineer is able to focus
on optimum performance in a specific application with the
knowledge that he can build the necessary molecules to achieve
it. Since synthetics cost considerably more than petroleum
based basestocks, they are generally reserved for problem
applications where conventional oils fail, or where the efficiency
benefits of synthetics recoup the initial cost.
The use of synthetic basestocks to solve lubrication problems
is not new. Various synthetics were developed and used extensively
during the second world war to prevent the oil from freezing
in the army tanks during winter combat. After the war, synthetics
were found to be essential for the new jet engines which ran
too hot for mineral oils, causing them to burn off rapidly
and leave deposits. These jet engines also had to be able
to restart at high altitudes where temperatures were often
-50F, so the oil had to pumpable at very low temperatures
as well as surviving the searing temperatures within the engine.
Indeed the modern jet engine would not exist today if not
for the simultaneous development of synthetic basestock technology
in the 1950s, and today virtually every jet engine in the
world operates exclusively on synthetic lubricants.
During the 1960s and 70s, synthetics moved steadily into severe
industrial applications where they solved high temperature
deposit problems with air compressors and oven conveyor chains,
and low temperature flow problems in arctic climates. New
synthetic chemistries emerged to meet and match every problem
industrial users could create, and there were many! Gradually
these expensive high-tech synthetic lubricants were entering
the mainstream and taken seriously as they proved their ability
to save money through reduced downtime, less maintenance costs,
extended equipment life, lower energy consumption, and higher
productivity. Focus shifted to the total cost of lubrication,
not just the cost of the lubricant, and synthetics were often
the winners.
Synthetic
automobile motor oils were introduced in the early 1970s with
such fantastic performance claims that they initially turned
the auto manufacturers and oil companies against the new unproven
products. While most claims were directionally valid, the
level of improvements were often exaggerated to the point
of fostering a "snake oil" reputation. Over the
ensuing years, the true benefits of synthetic motor oils were
identified and quantified to industry satisfaction and include
better high temperature stability, excellent low temperature
flow characteristics, lower volatility, increased fuel efficiency,
and extended life capability. Today car manufacturers and
oil companies alike readily acknowledge the superior performance
of synthetic motor and gear oils, especially in fleet or severe
duty usage. For the average car owner, however, driving conditions
are mild enough for conventional mineral oils to work satisfactorily,
which raises the question of whether synthetic benefits are
really needed for passenger cars and worth the higher price
tag. In most cases the combined improvements will repay the
higher initial cost, but since these improvements are not
readily perceived by the driver, market penetration remains
only a few percent after nearly thirty years. Synthetic motor
oil usage will likely accelerate in future years as engine
builders exploit the benefits in new engine design and ratchet
up oil performance through tighter specifications.
Today the use of synthetic lubricants is accepted, widespread,
and rapidly growing as their capability and cost efficiency
benefits become better known worldwide. Jet aircraft use synthetic
oils in the engines, hydraulic systems, instruments and landing
gears; compressors use synthetics in the crankcase and cylinders;
refrigeration systems use synthetics with the new environmentally
friendly refrigerants; truck fleets use synthetics in the
engine, transmission, and gear box; and the list goes on and
on. Wherever a problem exists with mineral oils or a potential
for improved cost efficiency uncovered, there is a synthetic
lubricant ready and able to step in and lower the cost of
total lubrication.
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