Alternatives to petroleum

Alternatives to petroleum-based vehicle fuels
Main articles: Alternative propulsion, Biofuel, Fuel economy, and Hydrogen economy
The term alternative propulsion or "alternative methods of propulsion" includes both:
alternative fuels used in standard or modified internal combustion engines (i.e. combustion hydrogen or biofuels).
propulsion systems not based on internal combustion, such as those based on electricity (for example, all-electric or hybrid vehicles), compressed air, or fuel cells (i.e. hydrogen fuel cells).
Nowadays, cars can be classified between the next main groups:
Petro-cars, this is, only use petroleum and biofuels (biodiesel and biobutanol).
Hybrid vehicle and plug-in hybrids, that use petroleum and other source, generally, electricity.
Petrofree car, that can not use petroleum, like electric cars, hydrogen vehicles...