In the United States, manufacturing equipment advancements is lagging because machines installed during the nation’s manufacturing heyday are durable and historically have been replaced only when replacement parts are no longer available or output requirements changed or increased. Once the decision to replace is justified, new machinery often has a lower mass per pound of production, which directly impacts lubricant performance requirements.
New machines that are smaller and which achieve higher output are purchased on the basis of cost, design efficiency and sustainability. The effect on the lubricant is that lower volumes of fluid are used, operating temperatures rise and thermal cycling rates increase, putting more thermal stress on the base oil molecules and additives.
Thermal cycling induces severe degradation in lubricants by causing oxidation, thermal cracking and additive depletion, leading to higher viscosity and sludge and varnish formation, though the viscosity increase can be counterbalanced by thermal cracking. Additive depletion also contributes to decreased thermal resistance. The heating phase accelerates oxidation and thermal degradation. The cooling phase causes condensation, which compounds with fluid degradation to form sludge.
Oxidatively and thermally stable base oils can slow the effect of thermal cycling. Polyalphaolefins, polyalkylene glycols and diesters derived from dicarboxylic acids — such as adipic and sebacic acid — and fatty alcohols all offer better oxidation resistance and thermal stability than mineral oils. Mineral oils rapidly decompose at approximately 350 degrees F, compared to 400 degrees, 450 degrees and 550 degrees for PAGs, diesters, and PAOs, respectively. As thermal decomposition occurs, however, diesters generate the fewest and softest deposits (which is best), followed by PAGs, mineral oils and PAOs.
Another enhanced lubricant property required from newer equipment is enhanced wear protection due to the increased operational loads. Enhanced wear protection can be accomplished with a mineral oil-based fluid as well as synthetics. If more than one type of fluid is capable of providing suitable performance, then cost of use becomes the deciding criteria.
The use of synthetic lubricants in industrial settings is increasing moderately. Driven by the need for higher machinery efficiency, reduced downtime and better performance under extreme temperatures and pressures, industries are shifting toward synthetic lubricants to enhance productivity and reduce maintenance costs for new equipment.
In its study Synthetic Lubricants Market (2023 – 2030), market research firm Grand View Research projected global consumption of synthetic industrial lubricants will grow for the rest of this decade but at a lower rate than synthetic automotive engine oils, for which it predicted a compound annual growth rate of 3.7%, both globally and in the U.S. The firm study concluded growth in the industrial segment will be slower because industrial equipment is replaced more slowly than automobiles and because emissions controls in manufacturing do not always require equipment replacement.
Another firm, Polaris Market Research, estimates the value of synthetic industrial lubricants will rise at a faster clip. In Industrial Lubricants Market Share, Size, Trends, Industry Analysis Report it pegged the value of the global segment at U.S. $57.05 billion in 2025 and forecasted compound annual growth of 3.8% through 2034.
In addition to thermal stability and oxidation resistance, synthetic lubricants can offer reduced friction compared to conventional products, reducing energy consumption and helping to reduce wear even while extending maintenance intervals.
Original equipment manufacturers are increasingly designing high-efficiency machinery that require advanced lubricants, pushing the use of synthetics in industrial gearboxes, compressors, hydraulic systems and other lubrication systems. Stringent environmental regulations are encouraging the use of longer-lasting, eco-friendly lubricants that generate less waste, improve energy efficiency and are manufactured with a lower carbon footprint.
Global industrialization and trade, particularly in the Asia-Pacific region, is driving adoption of high-performance lubricants in manufacturing, power generation, and heavy machinery. The high-performance lubricants are not always synthetics, but many are. The long-term benefits in reduced downtime and better performance make synthetic and other high-performance lubricants increasingly preferred. Market hesitation to further advance synthetic use due to cost, is answered with other high-performance lubricants that are blended with Group II base oils and highly stable additives.
Common Uses for Industrial Synthetics
Synthetics and other high-performing lubricants are used for enhanced deposit control, enhanced wear control, energy efficiency, extreme temperature tolerance and to lengthen service life. Following is a review of industrial applications where synthetic use has evolved to be common.
Air Compressors
One example of the evolved need for industrial lubricants is air compressors used at industrial facilities. In the 1930s, rotary screw and reciprocating compressors of that era typically delivered air pressure ranging from 70 to 90 pounds per square inch, and the common lubricant specification was a mineral oil-based fluid with oxidation inhibitors, anti-wear additives and good water separability.
Today plant air pressure and volume demands have increased to 90 to 200 psi, due to increased use of pneumatically controlled equipment, including robotics. The increase in air demand requires plant utilities operators to increase discharge air pressure, which increases discharge air temperature. To accommodate those temperatures, diester based fluids are used in high discharge pressure reciprocating air compressors and either PAO or glycol-ester based fluids are used in rotary screw air compressors. Better temperature control can reduce deposits in the compressor and reduce plant downtime.
High-pressure Hydraulic Systems
Large-scale metal pressing operations lead the way in placing more load carrying demand on hydraulic systems. In the 1920s, industrial hydraulic system demands ranged from 700 to 3,000 psi and fluid temperatures from 100 degrees F to 140 degrees. Current high-performing systems are pressurized up to over 10,000 psi and operate at temperatures ranging from 110 degrees to 180 degrees.
Fluid performance demands for such systems have been ratcheted in several ways. Higher temperatures and wider temperature ranges require more stability of viscosity, meaning fluids with higher viscosity index. Again, higher temperatures also necessitate greater varnish control — not only because of the increased potential for varnish formation but also because there is less tolerance for varnish in systems that use electronically controlled valves to provide instant response needed for precise performance. When varnish interferes with spool motion, hydraulic cylinders to not move as expected.
For all of these reasons, fluids blended from highly stable Group III mineral oils and synthetics such as PAOs are commonly used in modern industrial hydraulic systems.
High-temperature Bearings
Bearing configurations have not significantly evolved over the past eight decades, but the demand on both has increased with newer equipment. What has changed with bearing design is metallurgy and surface roughness. Outer and pillow block bearings are typically lubricated with grease but can be lubricated with oil. Inner bearings are typically lubricated with the inner component fluid. Bearing temperature is affected by speed, load, lubricant type and location. Synthetic lubricants protect bearings from premature wear mostly by resisting thermal degradation and viscosity reduction. Synthetic lubricant formulations have improved to maximize lubricant life and better mitigate wear.
Gearboxes
Parallel shaft gearboxes are mostly placed in service with mineral based extreme pressure lubricants. As production demands increase and downtime is expected to decline, synthetic gear oils are becoming more common so service intervals can be increased. Workloads increase for the gearboxes, causing more rolling and sliding forces that result in thinner lubricating films and more heat generated. The use of PAG and PAO gear lubricants can reduce deposits, wear and heat on the gear teeth by providing a thicker fluid film.
Worm Gearboxes
Worm gearbox lubrication requirements have not changed in that the rubbing wear between the steel worm gear and bronze bull gear must be kept to a minimum. Before PAOs and PAGs were introduced as lubricants in the 1940s, heavy oils compounded with animal fat were used to make the rubbing contact between gears slippery. Many operators are still using compounded oils in their worm gear boxes. Modern manufacturers of right-angle worm gear boxes mostly recommend either PAG- or PAO-based lubricants for service. The trend toward using synthetics in worm gearboxes started in the 1940s and is not expected to change in the future.
Mist Lubricators
The preferred lubricant to flow through mist lubricators in petrochemical plants has evolved from mineral oils to diesters. The lubricant in a mist lubrication system is atomized with compressed air soon after leaving the fluid reservoir. The atomized lubricant travels through pipes and tubes to near the service bearing where the mist is reclassified to a liquid form. Then drops of liquid are released to the bearing.
It was discovered in the 1940s that the reclassifiers in the mist distribution system get clogged with waxy residue from mineral based fluids and PAOs. This residue would range from waxy to an agglomeration of high-molecular-weight branched paraffins that would fall out of solution during the misting process. Diesters on the other hand are not made of long molecules and have inherent solvency. Thus, they do not tend to agglomerate or coagulate under any condition.
Mechanical Seals
Another use for PAOs that has evolved over the past eight decades was to reduce deposits on mechanical seal faces used in American Petroleum Institute Seal Plans servicing centrifugal process pumps in the petrochemical industry. Process fluids are typically heated for distillation or catalytic reaction. The labyrinth seals that contain the process fluid are designed with stationary steel and rotary carbon seal faces that are separated by a thin film of barrier fluid used to contain the process fluid at process fluid temperature. The ideal barrier fluid is a thermally stable fluid that can sustain short periods of exposure to 800-degree process fluids without leaving deposits from fluid thermal cracking or additive release at the seal faces. A lightly inhibited low-viscosity PAO is the best barrier fluid, so far.
Synthetic Grease Advancements
Many problematic component failures can be resolved with oils or greases made with synthetic base oils. Grease is simply an oil with a thickener designed to deliver and keep the oil at the bearing load zone. In most cases, once at the bearing load zone, oil is wicked out of the thickener for service and then reabsorbed in the thickener at the other end of the load zone. Specialty thickeners, like polyurea and calcium sulfonate complex, can be problem solvers because they are not formulated to release oil for service. The entire content flows through a bearing load zone, thus enhancing the stability and lubricating properties of the base oil.
In recent years, more development work has been performed on grease than on oils. For example, polyurea greases became popular in the 1980s, and calcium sulfonate complex thickened greases became popular for specialty service in the 1990s, and calcium sulfonate thickeners were developed later for better wear protection and thermal stability. In comparison, diester, PAG and PAO fluids have been in service since the 1940s.
Just as performance demands on lubricating fluids has and will continue to rise, the same can be said for grease. A synthetic base oil and the thickener need to be thermally stable enough where the grease will stay intact and in place while in service at temperatures up to 350 degrees. High-temperature greases with PAO base oils and complex thickeners are preferred in paper mills, wood pellet mills, feed mills, high-speed fans, steel mills and electric motors and in bearings near furnaces, mills and cookers. Grease manufacturers are constantly adjusting manufacturing sequences and components to improve the stability of grease for applications with long service intervals and high operating temperatures.
Frank J. Hayes is a senior product specialist with Citgo Petroleum Corp. He has earned certifications for Certified Lubricating Grease Specialist, Certified Lubrication Specialist, Machine Lubricant Analyst-I, Machineery Lubrication Technician-I and Oil Monitoring Analyst.