Machine elements operating under lubricated conditions will eventually fail due to high stresses and fatigue-related causes. In order to find optimum protective measures, it is important to understand how the stresses arise and what factors that influence their magnitude. With the current shift for more sever lubricating regimes, the role of tribo-improvers is becoming vital. At this point, the interplay between the chemisorption mechanism of various lubricant compounds and surface failure is not yet fully understood. To obtain a better understanding of this, a newly developed ionic structured tribo-improving additive, based on silicon, was investigated and benchmarked against conventional heavy-duty gearbox additives. A ball on disc device was operated under heavily loaded rolling/sliding conditions, at elevated temperature to simulate gear like conditions, and lubricating performance was subsequently evaluated in terms of friction and wear. Such results highlight the importance of properly designed lubricants for optimal tribo-performance under rolling-sliding conditions