And we all know about the latest Auto sales figures...."The automotive sector is moving toward lighter materials for production in order to reduce vehicle weights and improve fuel efficiency." http://www.trefis.com/stock/aa/articles/75044/demand-for-lightweight-autos-boost-alcoas-aluminum-business/2011-09-16
Another factual post.
Not only the engine block, but also many non structural components including interrior and exterior materials.
non structural are replaced by moulded FOAM