The carbon dioxide emission depends on car’s engine capacity and also on the type of fuel used. An average mid-size petrol car having 1600 CC engine would exhale about 185 grams of CO2, whereas a diesel car of the same capacity would produce around 150 grams, because diesel engines are significantly more fuel-efficient than petrol engines. However, diesels kick out more particulates, a major downside in metro cities where air quality is already a grave problem.
An electric car doesn’t give off any CO2, provided it is recharged using renewable electricity. If the electricity is that of a fossil-fuel power station, such car would be indirectly accountable for polluting environment with about 60 grams of CO2 per kilometer. Nevertheless, the electric car meets most green credentials.
Electric car (Wikipedia)
Fuel efficiency (Wikipedia)
Fuel economy in automobiles (Wikipedia)