| Operation & maintenance


fell, vibration signals dropped, and wear was reduced. Most strikingly, bench testing on an 850 kW drivetrain rig demonstrated a 0.8% increase in power output simply by switching lubricants. For engineers, these were robust indications, but not yet a case for widespread adoption. At Castrol, we knew we had to replicate these benefits in the field.


Designing a robust field trial Launched in September 2021, Castrol’s two-year field trial sought to back up the results gleaned from laboratory testing. Conducted on a US Midwest wind farm consisting of 133 GE 1.6 MW turbines, the trial was co-designed by independent consultants at Wood plc and ONYX Insight, with data audited by classification specialist DNV to ensure results were robust and unbiased. The methodology employed is the ‘side-by-side’ method that is integrated into IEC 61400 and utilised for comparing many other types of upgrades, not just lubricants.


Eight turbines were selected in matched side-by-side pairs to minimise atmospheric and topographic variables. Over two years, operators systematically alternated lubricants to minimise variables such as seasonality and equipment variation: some turbines began with Castrol products and switched to competitor oils midway, while others did the reverse. Two further turbines acted as controls, running the same lubricant for the full 2-year duration.


The dataset was exhaustive. More than 134 000 raw data points were collected via SCADA systems, oil analysis, and vibration monitoring. Over 97% of data was filtered out to eliminate anomalies caused by icing, grid constraints, or yaw misalignment, leaving a final dataset of 4 000 robust points for analysis.


The numbers that matter The outcome was clear. Against other OEM- recommended lubricants, Castrol’s low-friction formulation produced a +1.09% gain in AEP from cut-in to the ‘knee’ of the power curve, the wind-speed range most sensitive to drivetrain performance, and a mean +0.72% increase overall.


On the test site, this translated into roughly $1250 in additional annual revenue per turbine - a conservative figure, given the relatively modest 1.6 MW capacity and 27% capacity factor of the test turbines. With today’s larger models and higher-yielding sites, gains could be considerably greater.


For operators, these figures matter because they represent incremental power extracted without additional capital investment. Turbines require lubricants, but by using the best technology, measurable performance benefits can be unlocked with little-to-no additional cost. It’s not something that has to be bolted on – it’s part of routine maintenance.


Why small percentages make a big difference


A half-percent gain may appear marginal, but in the context of utility-scale wind economics, small


The field trial was conducted over two years with lubricants switched halfway Turbine 1


Turbine 2 Turbine 3 Turbine 4 Turbine 5 Turbine 6


Control 1 Control 2


Castrol Castrol Castrol


Competitor Competitor Competitor


Castrol Competitor Start of trial (September 2021)


percentages accumulate into major returns. Revenue impact: across a 100-turbine farm, an additional 0.72% AEP could equate to over $125 000 per year based on conservative assumptions. Scalability: with offshore turbines now exceeding 12 MW capacity, efficiency multipliers become even more significant. Lifetime effect: applied consistently over 20 years, efficiency improvements compound alongside reductions in wear and unplanned downtime.


Moreover, these benefits are achieved through a maintenance practice operators must already perform – lubricant changes – making the barrier to adoption minimal compared to structural retrofits or new hardware.


Lessons from the trial


Several engineering insights emerged from the trial that may shape future practice: Friction equals lost energy. Certain lubricants allowed gearbox temperatures to rise as friction consumed energy, diverting it into heat rather than electricity. By contrast, lower-friction formulations preserved more energy for the generator. Validation matters. By swapping lubricants mid-trial and running across two full seasonal cycles, the study controlled for turbine variance and seasonal wind density, ensuring results were not statistical anomalies. Benchmarking against reality. The close correlation between bench tests (+0.8%) and field trials (+0.72%) demonstrates how laboratory indicators such as coefficient of friction can be reliable predictors of real-world output.


Implications for the wind power industry


The trial represents a milestone for wind energy operations: one of the first independently validated demonstrations that lubrication technology can improve not only reliability, but also power productivity. For senior managers tasked with delivering more megawatt-hours per dollar invested, this offers a pragmatic lever. Compared with aerodynamic retrofits, control software upgrades, or structural modifications, advanced lubricants present an unusually low-cost, low-risk efficiency measure. They


Halfway switch (October 2022)


End of trial (November 2023)


require no new infrastructure, fit seamlessly into maintenance cycles, and can be deployed fleet- wide in short order.


Looking ahead: where now for lubrication and wind energy? As wind assets age, operators face dual challenges: extending turbine lifespans while extracting greater performance. Castrol’s advanced lubricants sit at the intersection of these priorities, reducing wear while incrementally boosting power.


Looking forward, three pathways emerge: Scaling to larger turbines: with the trial conducted on relatively small, 1.6 MW, machines, replicating results on today’s 5–10 MW platforms should show amplified financial impact.


Integration with digital monitoring: pairing lubricant performance data with predictive maintenance systems could allow operators to quantify real-time efficiency gains and adjust service intervals dynamically. Policy and market recognition: As regulators and offtakers focus increasingly on efficiency and LCOE reduction, incremental gains from lubrication may play a role in sustainability reporting and energy market competitiveness. For engineers and managers, the message is clear: the energy locked in friction losses is recoverable. In an industry where percentage points mean millions, lubricant choice is no longer just a matter of equipment protection – it can have a significant and lasting positive impact on energy productivity and revenue in the real world.


Competitor Competitor Competitor Castrol Castrol Castrol


Turbine maintenance. Monty Rakusen/ GettyImages


www.modernpowersystems.com | October 2025 | 29


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