The use of aluminum in automobiles can significantly reduce vehicle weight. This paper discusses factors that relate to why aluminum will be used in automobiles. These factors are fuel economy, fuel cost, federal regulations, and increasing weight trends. The cost of reducing weight is analyzed by the overall economy concept. Overall economy includes operating cost and initial purchase price. The role of inertia weight class and interacting weight reduction are discussed and exemplified by two vehicles. One is a production vehicle, the Feather Duster and the other is a prototype called the Charger XL. The substitution of aluminum into conventional applications sometimes requires the developing of new technology in design and manufacturing. These aspects of how aluminum will be used in automobiles is also discussed.