Is car consultant a good carrier after post graduation

Nope, rather a waste of an education.

Is car consultant a good career

Does that mean car sales? We don't use the word 'consultant' for car sales in the US, but I see it in other parts of the world.
Any sales job that pays on commission is going to depend on how good you are at your job, the type of cars you have to sell, and the reputation of the dealer. You might make nothing, you might make a lot.

So which career is best which is related to cars having good salary

Design Engineer, needing an advanced degree. Some are experts in internal combustion engines, some aerodynamics, some the latest electric car design.
This is all too vague. Tell us what degrees you have and what you want to do. Salaries vary around the world too. There are no quick easy answers.

Acutually m an engineering student.m doing mechanical engineering and aftr tis wll do mtech in automobiles.my interest is in cars so tats why I was curious about the jobs related to cars