I'm thinking of Australia specifically, since we have lots of aluminium but I suppose the same could apply to American cars since they are of similar conception. WI govts from about the 50s pushed/mandated the use of aluminium in mass produced cars? Lots of engine parts in Australian and US cars were made of cast iron but could have been made of aluminium (heads, manifolds etc), and I think a lot of other iron/steel parts could be made of aluminium with no adverse effect. How would the 1973 oil crisis look if our average car was a few hundred kilos lighter and more efficient? How fast would muscle cars get if aluminium heads were standard rather than an exotic option, and they were lighter in construction?