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Synthetic lubricants are produced from
chemical synthesis rather than from the refinement of
existing petroleum or vegetable oils. These oils are
generally superior to petroleum (mineral) lubricants in most
circumstances.
Synthetic oils perform better than mineral
oils in the following respects:
-
Better oxidation stability or
resistance.
-
Better viscosity index.
-
Much lower pour point, as low as -46°C
(-50°F).
-
Lower coefficient of friction.
The advantages offered by synthetic oils are
most notable at either very low or very high temperatures.
Good oxidation stability and a lower coefficient of friction
permits operation at higher temperatures. The better
viscosity index and lower pour points permit operation at
lower temperatures.
The major disadvantage to synthetic oils is
the initial cost, which is approximately three times higher
than mineral-based oils. However, the initial premium is
usually recovered over the life of the product, which is
about three times longer than conventional lubricants. The
higher cost makes it inadvisable to use synthetics in oil
systems experiencing leakage.
Plant Engineering magazine’s “Exclusive
Guide to Synthetic Lubricants,” which is revised every
three years, provides information on selecting and applying
these lubricants. Factors to be considered when selecting
synthetic oils include pour and flash points; demulsibility;
lubricity; rust and corrosion protection; thermal and
oxidation stability; antiwear properties; compatibility with
seals, paints, and other oils; and compliance with testing
and standard requirements.
Unlike Plant Engineering magazine’s “Chart
of Interchangeable Lubricants,” it is important to note
that synthetic oils are as different from each other as they
are from mineral oils. Their performance and applicability
to any specific situation depends on the quality of the
synthetic base-oil and additive package, and the synthetic
oils listed in Plant Engineering are not necessarily
interchangeable.
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