As others have pointed out, gasoline *has* been used as rocket fuel, but it has some disadvantages. Most of the time we use RP-1, which is *similar* to kerosene, diesel or Jet fuel, but is not quite the same. read more
Car engines can have fuel that have some impurities because it is ignited intermittently and is used to transform chemical energy into kinetic energy. Most Rockets ignite their fuel constantly and the resulting release of force from the chemical energy pushes the rocket away from the aperture of the rocket, even in vacuums. read more