Life cycle assessment (LCA) and manufacturing focused life cycle costing are used to evaluate the potential advantages of composites in automotive applications. The life cycle costs and environmental performance of several suitable lightweight polymer composites are quantified and compared against magnesium and steel for a representative component. The results indicate that weight reduction will not always lead to improved environmental performance. Materials offering high weight savings such as carbon fibres and magnesium have been shown to give limited or negative environmental benefits over their life cycles due to increased environmental burdens associated with their production. Lower performance materials such as sheet moulding compounds were found to perform better from a life cycle perspective despite not being recycled. Lighter weight vehicle components were found to be always more costly; however their use did lead to reduced costs for the consumer through lower fuel consumption. (C) 2011 Elsevier Ltd. All rights reserved.