Traveling

A roof rack or carrier provides additional cargo space and may allow you to meet your needs with a smaller car. However, a loaded roof rack can decrease your fuel economy by 5 percent. Reduce aerodynamic drag and improve your fuel economy by placing items inside the trunk whenever possible.
Avoid carrying unneeded items, especially heavy ones. An extra 45 kg in the trunk reduces a typical car's fuel economy by 1-2 percent.