Car materials in Maya are usually created from a layered shader with a base colour and a reflected colour and sometimes a third shiny coat, not to say you can't create a metal look from a blin though.
Realistic material creation is an art and something we all strive for .The main things you need to work on apart from not just having a uniform colour on the object (check out most things in reall life and you will see they have faults , wear and fade in the colour) is getting the specular and relectivity right for the material in question.All Maya materials can be adjusted and tweeked to death so it is possible to simlate almost anything, however getting it to look perfect takes time practice and experience.
you might also consider the roughness of a material and create a bump or displacement to simulate that.
Dirt maps can be applied to the Diffuse to create more realism also.