In the wind sector, equipment operates under dramatic temperature shifts, fluctuating loads and long service intervals, and lubricant behaviour can shape the rhythm of an entire maintenance strategy. When chosen and managed wisely, lubricants can help support the long-term health and efficiency of industrial equipment.

Understanding lubricants, from what they are to how they differ and how their condition changes over time, is a valuable skill for any operator, but navigating these choices requires expertise in the chemistry and engineering behind them. Gear oils, greases and hydraulic fluids may share a common purpose, but each type is formulated to meet specific operating demands, each containing a carefully balanced blend of base oils and additives designed to withstand specific stresses.

“In harsh operating conditions such as the wind sector, choosing the right lubricant should be a strategic decision,” says Kurtis Hartlen, Senior Sales Advisor at Imperial Oil. “The right lubricant can help to reduce friction, ensure proper operation under extreme temperatures (hot and cold), and support equipment efficiency.”

Understanding the main lubricant types

Among the most technically demanding lubricants used in industrial machinery are gear oils, which work in some of the harshest internal environments found in mechanical systems. Their viscosity must remain stable enough to maintain protective films in both high-torque and high-speed sections, and standards such as ISO and AGMA help manufacturers and operators align viscosity selection with expected operating conditions.

Lubricants as an Asset 2025, published by American Clean Power (ACP), explains that viscosity is an essential foundation for lubricant behaviour, shaping its ability to reduce wear and manage heat. Synthetic and mineral oils perform differently in this respect, with synthetic oils being engineered for improved oxidation resistance, thermal stability, and low-temperature performance, while mineral oils aim to provide protection under less severe conditions but typically do not offer the same resistance to degradation.

Additives further influence how gear oils behave, such as extreme-pressure agents, anti-wear additives, rust inhibitors, dispersants and antioxidants that are blended into the formulation to address specific challenges such as micropitting, foam formation and thermal degradation. The ACP report notes that balanced formulations are particularly important in applications with sustained high loads or temperature fluctuations. Without this balance, one performance requirement may be met at the expense of another, potentially leading to corrosion, deposit formation or equipment wear.

Greases, which are used in bearings, pitch and yaw drives and other components where oil would not remain in place, are lubricating oils thickened into a semi-solid. Their consistency is defined by the NLGI grade and determines whether they spread easily or remain firmly in position under load. Thickeners such as lithium soap, calcium sulfonate or their complex variants give greases their structure, and each thickener type has its own thermal and mechanical characteristics. Compatibility is a recurring concern, as mixing greases with different thickener systems can cause them to soften or harden unexpectedly, sometimes significantly reducing effectiveness. The base oil used also influences the film thickness, oxidation resistance and low-temperature performance. 

Hydraulic fluids form a third major category. Their viscosity must remain predictable across temperature swings, and their additive packages must protect pumps, servo valves and high-pressure components from wear. Seal compatibility is especially important, as some fluids may cause seals to swell or shrink, potentially leading to leaks, pressure loss or contamination. Following OEM recommendations is essential when selecting or replacing hydraulic fluids, particularly if a deviation from the manufacturer’s preferred formulation is being considered.

“At ExxonMobil, our OEM advisors work closely with manufacturers to design lubricants that meet, and often exceed, equipment specifications,” Hartlen explains. “For hydraulic systems, we consider temperature range, pressure demands, oxidative stability, cleanliness, seal compatibility, and wear protection. We then collaborate with OEMs and wind farm operators to test the fluids in the field before commercialisation to help performance and compatibility.”

Selecting lubricants for real-world conditions

Choosing between these lubricants requires close attention to the environment in which they will operate. According to the ACP report, there are several influential factors, including temperature range, load behaviour, exposure to moisture or contaminants, component design, and the overall lubrication method used in the system. Temperature is especially impactful, because a lubricant that performs well in moderate conditions may thicken excessively in cold climates or oxidise quickly in hot ones. Load patterns are also important considerations, with high torque and low speed requiring higher viscosity, while higher speeds demand lower viscosity.

OEM recommendations serve as a critical guiding framework that incorporate detailed knowledge of bearing tolerances, gearbox architecture, elastomer materials and thermal modelling. Choosing a lubricant that aligns with OEM expectations can help reduce compatibility issues and improve efforts to cope with the intended operating stresses.

Environmental and contamination challenges must also be considered. For example, moist and coastal environments may require lubricants with strong corrosion protection and water resistance. Systems exposed to dust or debris benefit from lubricants with enhanced dispersancy or from grease formulations that can hold contaminants away from critical surfaces. For enclosed systems such as gearboxes or hydraulic circuits, cleanliness is a defining factor in lubricant longevity.

Maintaining lubricants across their service lives

Maintenance practices determine how long lubricants can perform effectively, and relubrication intervals depend on temperature, cleanliness, system design and the lubricant’s inherent stability. Some formulations may support extended service intervals, but this is dependent on the conditions under which the lubricant is operating*. Insufficient lubrication can expose surfaces to wear, while excess material may increase heat or detract from energy efficiency. Achieving the correct balance requires careful observation and disciplined maintenance routines.

ExxonMobil collaborates with Poseidon Systems under a global marketing relationship to make advanced oil condition monitoring solutions available to Mobil™ customers and channel partners.

According to Bugra Kilincer, Global Commercial Marketing Advisor at ExxonMobil: “These solutions provide real-time lubricant health insights to support predictive maintenance and reliability improvement in wind operations. This co-branded offering complements Mobil lubricants and our application expertise, helping operators reduce unplanned downtime, optimise inspection schedules, and help improve total cost of ownership**.

“Our offline oil analysis, Mobil℠ Lubricant Analysis (MLA), remains a critical complement to real-time monitoring, validating lubricant health and supporting proactive maintenance decisions, while our Field Engineering Services (FES) team helps interpret monitoring data and implement corrective actions to help support asset life and performance.”

Regular oil sampling, laboratory testing and, where appropriate, on-line condition monitoring can help operators track viscosity trends, particle contamination, oxidation levels and additive health. Cleanliness is one of the strongest predictors of lubricant life, as even small increases in particle count can contribute to wear, while moisture ingress accelerates oxidation and corrosion. ISO 4406 particle codes classify contamination severity, acting as an important benchmark for understanding whether a lubricant remains within safe operating limits.

Oxidation resistance, thermal stability and corrosion protection also influence lubricant longevity. Oils and greases with stronger oxidative resilience can help maintain performance under sustained heat, while thermal stability reduces the likelihood of viscosity breakdown. Corrosion inhibitors support metal surfaces in resisting moisture-driven degradation. Together, these characteristics help lubricants maintain their intended protective roles throughout their service lives, provided they are kept clean and monitored appropriately.

Compatibility also becomes important when lubricants are changed or topped up. In oils, incompatible additive systems may produce unexpected reactions, while in greases the risk of incompatibility is even more pronounced. Compatibility should be verified through OEM guidance or laboratory analysis before consolidating or replacing lubricants. Failure to do so may lead to accelerated degradation, unexpected thickening, or separation of the lubricant components. 

ExxonMobil’s fill-for-life

Correct lubricant selection, stability under real-world operating conditions, balanced additive systems, and disciplined maintenance should form the foundation of a modern lubrication strategy. As wind turbines grow larger and more remote, operators have increasingly sought lubricants that can help minimise up-tower intervention, reduce exposure to hazardous maintenance conditions, and support gearbox reliability over longer intervals**.

Hartlen adds: “Fill-for-life technology in wind redefines what’s possible for long-lasting lubricant performance. By delivering exceptional oxidative stability and wear protection throughout the gearbox’s life, it helps reduce maintenance, minimize downtime, and cut oil waste.”

ExxonMobil has spent years developing and validating a gearbox lubricant architecture designed to support significantly extended service intervals under appropriate operating conditions**. Its How fill-for-life is set to keep turbines turning whitepaper explains how Mobil SHC™ Gear 320 WindPower is formulated using next-generation synthetic base fluids and an advanced additive system intended to deliver strong oxidation stability, micropitting resistance, load-carrying capability, and cleanliness retention. ExxonMobil also integrates rigorous used oil analysis, top-treat additive strategies, and in-situ flushing practices to help maintain oil condition over long service periods. This, in turn, helps operators to better monitor products over time as well as improve their understanding of how oxidation, viscosity, and contamination can influence service life.

Fill-for-life illustrates how the science of lubrication can be leveraged to help support long-term operational goals. To find out more, download the whitepaper below.

* Refer to OEM application requirements and oil drain intervals for your equipment

** Actual results may vary depending on the type of equipment used, its maintenance, operating conditions and environment, as well as any previous lubricants used.