What effect do loose filler caps have on a vehicle?

Answer: B — They waste money and fuel

Loose filler caps can lead to fuel evaporation, which can ultimately waste money and fuel. When the cap is not securely closed, gasoline can escape as vapour, contributing to a loss in the overall amount of fuel available for the vehicle's engine. This can not only increase fuel consumption because the engine has to work harder to compensate for the lost fuel, but it can also lead to increased emissions, as unburned fuel vapour enters the atmosphere. This wastefulness is both financially detrimental and environmentally harmful, making it vital for drivers to ensure that their fuel caps are tightened properly after refueling. The mention of effects on other aspects, such as engine performance or maintenance needs, is not accurate in this context. Loose filler caps primarily concern fuel economy and overall vehicle efficiency.