AMP - Aviation Maintenance Technician Powerplant Practice Exam

Which of the following has the greatest effect on the viscosity of lubricating oil?

1. Temperature

2. Engine rpm

3. Oil pressure

4. Altitude

The correct answer is: Temperature

The viscosity of lubricating oil is primarily influenced by temperature because viscosity refers to the thickness or resistance to flow of a fluid. As temperature increases, the kinetic energy of the oil molecules increases, reducing intermolecular forces and allowing the oil to flow more freely, thereby decreasing its viscosity. Conversely, as temperature decreases, the oil becomes thicker, increasing its viscosity. In practical terms, this means that the performance of lubricating oil in an engine is highly dependent on the operational temperature. At higher temperatures, engine components may require oil with lower viscosity to ensure proper lubrication and reduce drag, whereas lower temperatures can necessitate oils with higher viscosity to maintain effective lubrication until the oil reaches its operating temperature. While other factors like engine rpm, oil pressure, and altitude can have an impact on oil performance and behavior, they do not directly change the intrinsic property of viscosity in the way that temperature does. Understanding this relationship is crucial for selecting the right type of oil for different environmental conditions and engine operating scenarios.