Pack smart. Check your vehicle’s load capacity to make sure you aren’t putting too much weight in the car. On most new cars, the total weight you can carry is printed on the door placard inside the driver’s door jam. This load rating includes all the passengers and cargo. Be aware that fuel economy is reduced with extra cargo. Roof-top cargo boxes should only be filled with light bulky items. Heavy loads on the roof can make the vehicle more difficult to handle in emergency situations and increase the risk of a roll over. If not in use, remove the roof rack as if can significantly worsen your fuel economy.