Do you really need to lug around your entire tool collection, golf clubs, unused child safety seats and a library of books in your trunk? Every pound counts when it comes to fuel economy. According to the EPA, an extra 100 pounds in your vehicle could reduce your MPG by up to 2%. Keep only necessary items in your vehicle, like an emergency kit and one spare tire. You can also reduce drag on road trips by putting bulky and heavy items inside the car rather than on a roof rack.