What is a consequence of an APU operating in extreme temperatures?

When an Auxiliary Power Unit (APU) operates in extreme temperatures, it often leads to degradation of performance. This can happen due to several factors, such as the effects on the lubricating oil, the operational efficiency of components, and how well the system can maintain optimal performance under stressful environmental conditions. In extreme heat, for example, the APU may struggle with cooling, leading to higher temperatures in engine components that can accelerate wear and overall performance loss. Similarly, in extreme cold, fuel viscosity changes can affect combustion efficiency and start-up performance. Thus, operating outside of recommended temperature ranges can hinder the APU's functionality and reliability, resulting in suboptimal performance during critical operations.