The effects on fuel economy, emissions, passenger car safety and other varaibles due to the installation of light-weight Diesel powerplants were studied. Experimental data was obtained on naturally aspirated and turbocharged Diesel engines installed in subcompact and compact passenger vehicles. The data include fuel economy as a function of engine type and horsepower, transmission layout, vehicle inerta weight, and of regulated emission constraints. Unregulated emissions have been characteristized during the course of the work. The compatibility of the Diesel engines studied with passenger car structures incorporating advanced frontal crashworthiness capabilities was analyzed and demonstrated with the Integrated Research Vehicle (IRVW).