The Magnesium Front End Research and Development (MFERD) project under the sponsorship of Canada, China, and USA aims to develop key technologies and a knowledge base for increased use of magnesium in automobiles. The primary goal of this life cycle assessment (LCA) study is to compare the energy and potential environmental impacts of advanced magnesium based front end parts of a North American-built 2007 GM-Cadillac CTS using the current steel structure as a baseline. An aluminium front end is also considered as an alternate light structure scenario. A “cradle-to-grave” LCA is conducted by including primary material production, semi-fabrication production, autoparts manufacturing and assembly, transportation, use phase, and end-of-life processing of autoparts. This LCA study was done in compliance with international standards ISO 14040:2006 [1] and ISO 14044:2006 [2]. While weight savings result in reductions of energy use and climate change emissions during the use phase of the car, the impacts of autoparts manufacturing and end of life recycling phases of lightweight autoparts designs are substantial as well. Pathways for improving sustainability of magnesium use in automobiles through material management and technology improvements including recycling are also discussed. Mg lightweight designs contribute to the largest use phase total primary and climate change savings over the vehicle's life time. Sustainably manufactured and recycled large magnesium structural parts can provide environmental benefits in terms of climate change emissions and consequently energy use vis-à-vis steel within the expected life of the vehicle. Overall, the aluminum lightweight design showed the best breakeven vehicle distance travelled from primary energy use and climate change perspectives within the vehicle's life time.