Think about what’s in your car’s trunk — or in the back seat. It’s smart to carry some rock salt and perhaps a shovel during the winter months, in case you get stuck on ice, but if you’re carrying all kinds of heavy things for no good reason, know that they’re making your car work harder. That uses more gas and costs you more — as much as $0.03 per gallon more, for every 100 pounds of stuff. So move that collection of sledgehammers and anvils and sewing machines out of your trunk! One heavy item that really should not be in your trunk is a container of gasoline, for whenever you run out of gas. That’s dangerous.