How does cargo weight affect fuel efficiency?

When considering how cargo weight impacts fuel efficiency, it is important to understand the relationship between weight and energy expenditure. Heavier loads necessitate more energy for the vehicle to move, which directly translates to a decrease in fuel efficiency. This is because the engine has to work harder to overcome the inertia of the additional weight, especially during acceleration and while climbing hills.

In contrast, lighter loads generally require less energy, allowing for better fuel efficiency as the vehicle can operate more efficiently. The other options suggest either no effect or an improvement in fuel efficiency with increased weight, which does not align with the principles of physics and energy consumption in vehicles. Therefore, recognizing that heavier loads decrease fuel efficiency due to the increased energy requirements is crucial for understanding fuel economics in trucking.