More efficient engines usually operate at higher temperatures, and this can require better oils. Modern oils have been developed to run not only at higher temperatures, but also to reduce maintenance costs.

For example, Rolls-Royce is a key industry player within the Society of Automotive Engineers for the evaluation, approval and management of change for gas turbine lubricants. “We work closely with turbine-engine oil manufacturers to develop the next-generation polyol ester lubricants for current and future gas turbine engines,” a Rolls fuel expert explains.

Currently, Rolls has evaluated and approved AS5780 HPC-grade—for high-performance capability—turbine lubricants for use in certain turbine engine applications. HPC lubricants have been approved for a number of Rolls engines. Specific brands have been approved for applications in  helicopter engines and small, medium and large fixed-wing turbine powerplants. Operators must consult manuals to determine which brands of HPC oils have been approved for their engines.

The Rolls expert says HPC lubricants improve the performance of modern engines, which run at hotter temperatures than their predecessors and are operated over longer intervals between maintenance checks. HPC-grade turbine oils were developed by the oil-products industry specifically to improve engine performance and lengthen engine life. They increase thermal stability, or the resistance of molecules to decomposition at high temperatures, and are more compatible with elastomers or rubber. HPC oils also resist oxidation better and thus decrease carbon deposits within the engine. This reduction in carbon deposits leads to longer engine time on wing and reduces maintenance cost, so life-cycle costs are decreased.

The Rolls expert says the current generation of turbine lubricants, including HPC oils, typically do not reduce the weight of lubricants. But in the future, lubricating systems themselves might be redesigned to be more compact, thus operating with smaller volumes of oil while still meeting engine requirements. This would reduce lubricant weight and total engine weight.