Why should the fuel tank not be overfilled during refueling?

The correct choice emphasizes the importance of allowing for fuel expansion, which is essential when refueling a vehicle or equipment that utilizes a fuel tank. Fuels typically expand as they warm up, and if the tank is overfilled, there may not be enough space for this expansion, potentially leading to spillage. When the fuel expands beyond the tank's capacity, it can overflow, creating safety hazards and environmental concerns.

Furthermore, proper fuel level management is crucial to the overall efficiency and safety of the equipment. Overfilling can lead to issues such as vapor lock or system malfunctions, which can affect performance and lead to costly repairs. Thus, leaving room for expansion is an important part of safe refueling practices. While preventing spillage and maximizing efficiency are also relevant considerations, the main reason to avoid overfilling hinges on ensuring there is adequate space for fuel expansion within the tank.