Feature article on synthetic lubricants written by
Richard Stewart for Castrol.
'Liquid Engineering' Yields
Lubricants For Every Need
Synthetic Oils Outperform Refined Products
in High-Heat, High-Stress Applications
Synthetic-based lubricating oils, fluids and greases
are becoming the lubricants of choice in many
industrial and automotive applications. Superior
performance characteristics make them better
suited than traditional lubricants for use in today's
hotter-running engines and highly stressed
automotive components. And since motor oil has
become an important factor in the reduction of
diesel engine emissions, engine manufacturers
have become closely involved in its development.
Whether the base stock is mineral or synthetic,
modern high-performance lubricants are formulated
to perform a variety of tasks beyond simply
reducing friction and wear. They must also control
the formation of deposits, suspend contaminants,
protect against corrosion, clean the components,
and maintain the desired operating temperature.
Additives such as anti-oxidants and dispersants
provide many of the special properties that are
required by an application.
Refined vs. Synthesized
Conventional oils, refined from crude petroleum,
contain molecules of various size, shape and
chemistry, along with impurities such as nitrogen,
sulphur and metals. Removing all of the unwanted
compounds is impossible. Synthetic lubricants are
formed by chemically synthesizing relatively pure
materials such as polyalphaolefins (PAOs), esters
and polyglycols. The results are predictable,
resulting in molecules of uniform size, shape and
the desired chemistry. Further processing by
polymerization and other means produces
lubricants with specific properties.
"Liquid engineering" is the term used by Castrol
North America to describe the process of custom
formulating lubricants to meet the exact needs of
customers. "Each application has its own set of
lubrication requirements, varying by load, speed,
temperature, and a range of internal component
differences," explains Dan Deneen of Castrol's
Specialty Products Division. "These factors all
impact the selection of the right lubricant for the
Deneen, who works primarily with automotive
OEMs and major component suppliers, sees a trend
toward the use of more synthetic and partial
synthetic lubricants (addition of synthetics to
mineral-based oils) by Castrol's customers. His
division is the world's largest supplier of specialty
lubricants, offering products to lubricate every
moving part on a vehicle, as well as two-stroke
motor oils and biodegradable lubricants, according
Advantages of Synthetics
"In the automotive industry, there's an underlying
trend to go toward synthetics or partial synthetics
due to higher temperatures under the hood," he
reports. "Since vehicles have become more
aerodynamic, less air is flowing through the engine
compartment and over the powertrain. That means
less cooling, which results in hotter lubricants."
According to Deneen, synthetic lubricants offer
reduced friction and can operate more efficiently
over increased temperature ranges than petroleum-
based lubricants. They have a higher viscosity
index and change less as temperature rises and
falls. Plus they tend to operate cooler — as much
as 50 degrees F. cooler than mineral oils, he adds.
Synthetics are thermally more stable and do not
oxidize or break down as quickly at high
Deneen feels that the ability of synthetics to
resist oxidation is a significant advantage over
conventional lubricants. When conventional oils
oxidize, they leave residues of carbon, which
contaminate the lubricant. Synthetics also have
low volatility and do not vaporize or boil off as
the temperature rises, he says.
Cost-Effective for Trucks
Synthetic gear oils have found widespread use
in commercial vehicles, in transmissions and
axles. The ability of synthetics to operate cooler
and resist oxidation has enabled several
manufacturers of heavy-duty transmissions and
axles to offer extended component warranties
when synthetic lubricants are used, up to seven
years or 70,000 miles.
Since synthetic lubricants are more stable than
mineral oils, longer change intervals for
transmissions and axles are possible, reducing
scheduled maintenance for operators. Typically,
the required flush and refill interval for a heavy-
duty truck transmission is 50,000 miles with
conventional lubricants. That interval can be
extended to 250,000 miles with synthetics, which
means less vehicle downtime and less dirty gear
oil for disposal, Deneen points out.
Unscheduled downtime can be minimized by
using synthetics, too, since the life of components
and seals is extended, due primarily to the lower
temperature of the lubricant. "When you reduce
the temperature of the bulk oil, the seals last longer
and the bearings last longer," he says. "Heat is the
enemy of moving equipment. The higher the
temperature, the shorter the life of the parts.
Longer component life is a real benefit of
Using synthetics can provide cost savings, too.
"If a manufacturer can eliminate the need for an
oil cooler on a new transmission design by
switching to a synthetic lubricant, the cost savings
in tooling and labor can be great," notes Deneen.
"While the synthetic lubricant costs more to buy,
the overall savings made possible by the lower
operating temperature of the synthetic oil will be
Deneen typically deals with customers who have
problems requiring lubrication solutions. "A design
engineer might come to us with a transmission
that doesn't shift right during cold weather. Maybe
it's sluggish in certain gears," he says. "We'll
engineer a lubricant that solves the problem."
Since low-temperature fluidity is a characteristic of
synthetic lubricants, a solution might be the addition
of a synthetic to a mineral-based transmission
fluid. That can improve low-temperature operation
and improve fuel economy at extreme winter
temperatures. Partial synthetics such as this are
used to help contain costs while reaping some of
the benefits of synthetics.
"We recommend that people use synthetics only
when they need to, because they are more
expensive than mineral oils," notes Deneen.
"Specialty mineral-oil lubricants can be designed
for their applications, at a lower cost than
synthetics. Our aim is to produce a lubricant that
meets the customer's physical parameters and their
Despite the higher cost, Deneen expects to see
synthetics continue gaining ground over conventional
lubricants. As engines become smaller, more efficient,
and more powerful, operating temperatures will
continue to rise. Vehicle design will continue to push
the aerodynamic envelope to slice through the air
quicker, resulting in less cooling air. Then the benefits
offered by synthetics will begin to outweigh the cost
disadvantages, he feels.
For more information, contact Dan Deneen at
Castrol North America, Specialty Products Division,
240 Centennial Avenue, Piscataway, NJ 08854.
Telephone: 800-OEM-LUBE or (908) 457-0037.
Fax (908) 457-8835.