The pour point of #2 oil refers to?

The pour point of #2 oil is defined as the lowest temperature at which the oil remains fluid and can still flow. This measurement is crucial because it indicates the temperature threshold below which the oil may solidify or become too viscous to pump effectively. For heating purposes and other applications, knowing the pour point helps in determining safe storage conditions and effective operation of equipment using the oil. Understanding this aspect is essential for maintaining efficiency and reliability in systems using #2 oil.

The other options, while relevant to oil characteristics, do not accurately define the pour point. Ignition temperature refers to a different property, highest flow temperature does not align with the pour point definition, and optimal operating temperature is separate from the characteristics related to flow and solidification.