PRODUCT GUIDE FOR
S Y N T H E T I C
Synthetic lubricants offer a number of operational advantages over mineral-based products
across a wide array of applications, including bearings, gearboxes, compressors, vacuum
and diaphragm pumps, rotary shaft seals, valves, hydraulic systems, and instrumentation.
Synthetics are the logical choice if:
Peformance demands are beyond petroleum product capabilities
Equipment failure of excessive downtime is traceable to ineffective lubrication products of practices
High or low temperatures are encountered (-75 to about 500 F)
Situations exist in which conventional products are ineffective.
Some man-made lubricants cause less metal wear because they create a lower coefficient of
friction in the load zone of non-conforming surfaces. This condition cuts maintenance,
parts replacement, and energy costs. In addition, synthetics provide long life because of
enhanced thermal and oxidative stability; and minimal sludge, corrosive, and deposit
formations because of high temperature oxidation stability.
The major drawback to the synthetic approach in an appropriate application is a
significantly higher initial cost three times or more. However, this cost is usually recovered
over the extended life of the product six times or more. Also, systems subject to leakage or
contamination are not usually good candidates for synthetic products.
The chart on the following pages serves as a guide to selecting and applying synthetic oils
and greases. The listings are based on information supplied by the 67 companies and are
categorized according to viscosity. However other important variables should be
considered when selecting and applying the products. These factors include pour and flash
points, demulsibility, lubricity, rust and corrosion protection, thermal and oxidation
stability, antiwear properties, compatibility with seals and paints, and compliance with
various testing and standard requirements.
The products presented in each category are not necessarily interchangeable or compatible.
These two features depend on an assortment of interrelated factors, and each situation
requires an individual analysis.
A properly selected synthetic does the same job as any mineral oil, if not better, but no
single product exceeds petroleum in every characteristic. Nevertheless, it is possible to
formulate synthetic lubricants containing those features that are most important for a
specific application. The result is an optimum compromise that petroleum products cannot
Performance characteristics of synthetic lubricants come from the physical and chemical
properties of the base fluids, and chemical properties of the base fluids, and the effects of
additives introduced into the final product. Physical and chemical qualities include
viscosity-temperature behavior, low temperature fluidity, volatility, compatibility with
paints and elastomers, ability to dissolve chemical additives, compatibility with petroleum,
and hydrolytic stability. Additives are included to influence to a greater or lesser degree,
oxidation stability, load bearing ability, and corrosion protection.
Table I shows the relative performance characteristics of seven general types of synthetic
lubricants and a paraffinic mineral oil.
There are several classes of synthetic lubricants. The most common are synthesized
hydrocarbons, such as polyalphaolefins (PAO) and dialkylated benezenes. These products
are the closest to the performance characteristics of mineral oils and are compatible with
them. Other commonly used synthetic lubricants are organic esters, including dibasic acid
esters (diesters) and polyol esters; phosphate esters; polyalkylene glycols (polyglycols); and
SYNTHETIC HYDROCARBON FLUIDS (SHF) equal or exceed the best lubricating
properties of mineral oils, but without the drawbacks. These synthetic base fluids are
manufactured from specific chemical compounds that are often petroleum derived. The
SHF base fluids are made by chemically combining (synthesizing) various
low-molecular-weight compounds to obtain base stocks with predictable desired properties.
These man-made fluids are available in several viscosity grades and operate over a wide
temperature range. The products serve as engine and turbine oils, hydraulic fluids, gear
and bearing circulating oils, and compressor lubricants. SHF's are wax free, offer excellent
hydrolytic and chemical stability, and provide low volatility.
ORGANIC ESTERS have shear-stable viscosities over a wide temperature range (-l00 to
400 F), high film strength, good metal wetting, and low vapor pressure at elevated
temperatures. Organic esters easily accept additives, enhancing their applicability for
finished product formulations such as crankcase oils and compressor lubricants.
POLYOL ESTERS feature many of the advantages associated with dibasic acid esters,
but perform at even higher temperatures. These esters are applied as high temperature
chain lubricants and in industrial turbines.
PHOSPHATE ESTERS are organic lubricants well suited for fire resistance
POLYGLYCOLS offer excellent viscosity and temperature properties, and resist sludge
buildup. Formulated products are used in applications from -40 to 400 F, and are low in
toxicity. Because of their solubility characteristics, polyglycols are well suited for
lubricating gears and bearings and compressors handling hydrocarbon gases.
SILICONES are chemically inert, nontoxic, fire resistant, and water repellant. The
products have low pour points and volatility, good low-temperature fluidity, and good
oxidation and thermal stability up to very high temperatures.
A disadvantage of silicones is their low surface tension, which permits excessive spreading
on metal surfaces. In addition, this product offers poor response to wear and
It is important to remember that synthetics are as different from each other as they are
from petroleum lubricants. The performance of a synthetic and its applicability to any
individual situation depends on the quality of the synthetic base stock and the additive
Table II outlines several major applications for synthetics.
Suitability of a specific synthetic for a given application often depends on the chemical
compatibility with system components. In general, synthetic hydrocarbons, like PAOs,
match well with seals, elastomers, paints, and plastics, while esters may not.
Compatibility should be checked with the lubricant previously used in the equipment.
Some synthetics are compatible with mineral oils; others are not. Polyglycols are not
generally miscible or compatible with mineral oils. Phosphate ester hydraulic fluids are not
miscible with water and waterglycol hydraulic fluids. The compatibility of the thickeners
must be considered when choosing synthetic greases.
It is not usually advisable to mix various types of synthetics. The system should be drained
and flushed when changing to a different lubricant.
It is advisable to consult a manufacturers's representative before introducing a synthetic to
guarantee that the right product is selected, and to obtain the maximum benefits from its