Nowadays, scientists are studying some alternatives to answer this question which is one of the most important problems.

 So I think :the best alternative is using another kind of energy like Solar Energy,the Eolian...
    The cars of the future must use these kinds of energy to produce less polution. Some cars are using only electrical energy now:
BOLLORE's BLUE car, Lightning's GT, Venturi's ECLECTIC..... There are also some less which use Solar Energy. But Venturi's ECLECTIC, ASTROLAB, Polytech's BELENOS are using solar energy. BELENOS won the PHEBUS 2007, which is a rallye of solar vehicles! " So it's possible to have a car which doesn't use any petrol or diesel. And the engineers are trying to improve these new technologies so let's wait and see!!

Each one can use solar energy at home to reduce our electricity using. This will also reduce the pollution.

Thank you for your attention.