Potential future car technologies include new energy sources and materials, which are being developed in order to make automobiles more sustainable, safer, more energy efficient, or less polluting.
One major problem in developing cleaner, energy efficient automobiles is the source of power to drive the engine. A variety of alternative fuel vehicles have been proposed or sold, including electric cars, hydrogen cars, and compressed-air cars.
Various technologies have been developed and utilized to increase the energy efficiency of conventional cars or supplement them, resulting in energy savings.
* Regenerative braking recaptures energy that would otherwise be lost as waste heat from the brake pads.
* BMW’s Turbosteamer technology to harness the heat generated by conventional internal combustion engines and use it to generate mechanical energy , resulting in a 15% increase in fuel efficiency. 
* Utilization of waste heat from D.W. as useful mechanical energy through exhaust powered steam, stirling engines, thermal diodes, etc..
* Using computational fluid dynamics in the design stage can produce vehicles which take significantly less energy to push through the air, a major consideration at highway speeds. The Volkswagen 1-litre car and Aptera hybrid car are examples of ultra-low-drag vehicles.
* Duraluminum, fiberglass, carbon fiber, and carbon nanotubes may totally replace all steel in cars (potentially improving lightness and strength). Aluminum, carbon fiber and fiberglass are currently being used more in cars today.