El_Phil said:
Eh? Last time I checked the chassis of a car was still steel and the bodywork was metal of various types (sports cars use plastic/fibreglass for lower weight). The engine block is still steel/ally depending on makers preference or spec.
You must have not checked in in the last 15-20 years.
Most cars these days, at least as sold in the US, have bodies consisting almost entirely of plastic and/or fiber glass. The frame and necessary parts of the engine are still steel, but that is about it. Its a way to not only make the car cheaper to build, but also to make it lighter, thus increasing gas mileage.