Which of the following is NOT a high-level source of contamination for lubrication?

The reason temperature is not classified as a high-level source of contamination for lubrication lies in its role in the lubrication process rather than as a direct contaminant. Temperature is a physical factor that can influence the lubrication system's performance by affecting the viscosity of the lubricant or causing thermal degradation over time, but it does not introduce foreign materials or particles into the lubricant.

In contrast, the other options represent direct sources of contamination. Built-in contamination refers to materials or particles that may be introduced during the manufacturing process or assembly, while ingested contamination involves particles that enter the lubrication system from the external environment, such as dirt or moisture. Generated contamination includes wear debris or by-products created during the operation of machinery that can compromise the lubricant's effectiveness.

Understanding these distinctions helps to identify appropriate contamination control measures and maintain lubrication quality, ultimately contributing to enhanced equipment reliability and performance.