To improve fuel efficiency, what should be avoided while driving?

Carrying cargo on the roof can significantly impact fuel efficiency due to aerodynamic drag. When cargo is placed on the roof, it creates additional wind resistance as the vehicle moves. This drag forces the engine to work harder to maintain speed, resulting in increased fuel consumption. In contrast, keeping the cargo inside the vehicle minimizes this effect, allowing for a smoother airflow around the car, which can improve fuel efficiency.

Frequent stops, driving with windows up, and using GPS for navigation do play roles in a vehicle's overall efficiency, but they do not have the same direct impact on aerodynamic drag as carrying cargo on the roof does. For example, while frequent stops can lead to increased fuel use related to acceleration, it doesn't have the same consistent effect as the added drag from rooftop cargo. Similarly, having the windows up can help maintain better aerodynamics compared to having them down, but it is less impactful than the roof cargo scenario. Lastly, using GPS is a tool for navigation that helps drivers find the most efficient routes, thus potentially optimizing fuel use overall.