Aluminum's low density, about one-third that of steel, makes it extremely lightweight. This property is crucial in various applications where weight is a critical factor. As you mentioned, aluminum's lightweight properties contribute to improved fuel efficiency in transportation applications. When vehicles, aircraft, or even bicycles are lighter, they require less energy to move, resulting in reduced fuel consumption or increased battery life in electric vehicles. Aluminum has a natural oxide layer that forms on its surface when exposed to air.