Operations and maintenance (O&M) expenses account for approximately 10–25% of the total cost per kWh over a turbine’s lifetime.[i] Gearbox maintenance is a major part of these costs, and frequent oil changes have historically been a key contributor. In the early days of wind turbines, gear oils typically needed replacing every three to five years, meaning multiple oil change operations over a turbine’s lifespan.

Each oil change involves bringing the turbine offline, sending technicians up-tower, handling large volumes of new and used oil, and dealing with the logistics of equipment and weather. This is even more challenging for offshore turbines, where adverse conditions and logistical issues potentially delay maintenance for days, driving up downtime costs.

Engineering gear oils for lifelong performance

Mobil SHC™ Gear 320 WindPower is an advanced synthetic gear oil designed specifically for extreme longevity under typical wind turbine conditions. Its next-generation polyalphaolefin (PAO) base oil technology is a highly stable synthetic base stock that resists thermal and oxidative breakdown. This stability means the oil’s foundation is robust; the main limiting factor becomes the additive package, which gradually depletes with use. [ii]

To address additive depletion, Mobil SHC Gear 320 WindPower uses a balanced, fortified additive system that provides excellent protection and is formulated to help extend gear and bearing life in enclosed gear drives operating under extreme conditions of load, speed and temperature. The formulation provides strong protection against micro-pitting, corrosion, foam, and air entrapment across a wide temperature range (-35 °C to 100 °C), providing reliable lubrication from cold-start through peak output. [iii]

Another pillar of the fill-for-life design is oil cleanliness and filtration. The gear oil is delivered ultra-clean, and the turbine’s lubrication system continuously fine-filters the oil during operation. This fine filtration removes contaminants and degraded materials that would otherwise accumulate, forcing an oil change. 

ExxonMobil has also developed a complementary top-up additive called Mobil Xtra™ EP WT Top Treat. At certain intervals, operators can inject this booster to replenish critical additives in the oil, refreshing the lubricant and extending its life.

Proven reliability: Testing and DNV certification

ExxonMobil’s developers undertook extensive testing to validate Mobil SHC Gear 320 WindPower, including accelerated life testing in the lab. This involved ageing the oil under elevated stress conditions and correlating the results with real-world used oil samples from wind turbines of varying ages. Field trials have also been underway since 2020 to observe the oil in operational turbines.

To leave no doubt, ExxonMobil sought independent verification. In September 2024, Det Norske Veritas (DNV) reviewed the evidence and issued a Conformity Statement endorsing the fill-for-life capability when used with the prescribed top-up additive strategy. This makes Mobil SHC™ Gear 320 WindPower one of the first gear oils to earn such a certification. It was also the first lubricant certified by DNV not to contribute to white etching crack (WEC) formation, a particular type of bearing damage in wind gearboxes.[iv]

Understanding the benefits: Cost savings, uptime, and reduced waste

Eliminating routine oil changes means saving on the purchase of hundreds of gallons of replacement oil, on waste oil generation, and on the labour and equipment costs of oil-change crews. Furthermore, with no need to shut down turbines for oil changes every few years, operators potentially avoid those periods of lost production*.

Cutting out regular up-tower oil change jobs, especially offshore, means fewer trips in challenging weather and less heavy lifting at height, helping to reduce hazardous work conditions. Using one oil fill for decades can potentially help reduce the environmental footprint associated.

Overall, early adopters of fill-for-life technology may potentially gain financially and operationally, as fewer interruptions and lower maintenance costs, and improve project profitability*. In the coming years, we can expect fill-for-life lubrication to become a new standard, keeping turbines turning with maximum efficiency, minimal downtime, and greater confidence for owners and operators.

*Maintenance costs may vary and are based on application-specific operating conditions. Not a guarantee of financial performance. Actual results can vary depending upon the type of equipment used and its maintenance, operating conditions and environment, and any prior lubricant used. Refer to OEM application requirements and oil drain intervals for your equipment.

[i] https://www.wind-energy-the-facts.org/operation-and-maintenance-costs-of-wind-generated-power.html

[ii] https://www.mobil.com/en-gb/industrial/pds/gl-xx-mobil-shc-gear-320-windpower

[iii] https://www.mobil.com/en-gb/industrial/pds/gl-xx-mobil-shc-gear-320-windpower

[iv] https://www.mobil.co.uk/en-gb/product/mobil-shc-gear-320