The paper is dealing alternative non-polluting engines for driving cars. Only air-water system components are used as working and heating fluids. Through optimization processes, gaseous nitrogen, oxygen and hydrogen, from air and water, may be obtained at acceptable energy (solar or nuclear) need, to be converted in liquid form at low cost. Using such cryogenic liquid fluids, solutions are proposed for car heat engines not producing air pollution and greenhouse warming, i.e.: high pressure and temperature multiple expansion reciprocating engine, with water steam as working fluid produced in a H2/O2/H2O combustion chamber. In a closed cycle, water steam is condensed by an air-radiator; superheated and reheated nitrogen in a double acting reciprocating gas expander, whose open cycle get heat from hydrogen-air combustion.