Which of the following does not affect pump efficiency?

Pump efficiency refers to how effectively a pump converts the energy supplied to it into the ability to move fluids. Factors that can influence this efficiency include the internal condition of the pump, such as wear and tear due to pump age, the diameter of the hoses used in the system, and the elevation of the discharge point, which can impact the pump's ability to generate adequate pressure.

The type of fuel used is not a direct factor affecting the pump's mechanical efficiency. Fuel type primarily matters in relation to engines that may drive the pump, but the efficiency of the pump itself, in terms of moving water or other fluids, depends on hydraulic factors rather than what fuel type is powering the engine. Therefore, it is correct to say that the type of fuel used does not affect pump efficiency.