Car materials these days are chosen to reduce weight, save costs and make cars more environmentally friendly. Steel as a car material today is found only in their frames, and as my Saturn dealer advised me, in "the body parts that face the sky", such as the car's hood, trunk lid and the roof. The balance of the car's body is a composite of fiberglass and polycarbon material, which is lightweight and shock-absorbent, too.
Solid steel and cast iron are no longer the car materials preferred for car engines any more. These metals are too valuable and too heavy to use in the engine, which is subject to corrosion, rust and metal friction at high temperatures. Aluminum is now the standard car material for engine blocks in virtually every car made.
Petrochemical engineering is the source of most car materials for the interiors of modern cars. They represent a triumph over nature as they are water-resistant, preventing the growth of mold and mildew. Polyvinyl chlorides, polypropylene ultra-fine fibers and other synthetic materials make up the car's interior from the dashboard cover to the floor mats. Some manufacturers are using natural fibers such as hemp for lining and cushioning the headliner (where the sun visors are attached). A large part of the car's interior is now lined with sound-absorbing cushions of polypropylene.