Mechanical Engineering

Automobile engineering is a branch of Mechanical engineering, where you'll deal mostly with automobile, whereas in Mechanical engineering, you'll deal with all machines and its design and then many more basics. But literally both are same, no big difference. Syllabus of Automobile engineering overlaps with Mechanical engineering between 80 to 90%. Compulsory courses on engineering drawing, workshop, instrumentation, Thermodynamics, Strength of material , theory of machines, heat transfer, Refrigeration etc are common in both Mechanical and Automobile engineering but additional like automotive chassis, engine, dynamics, body engineering suspension, transmission, automotive electronics & electrical are separate .
Automobile engineering is a niche branch thus it has less opportunities in comparison to Mechanical engineering graduates. Mechanical engineers are employed in Automobile industry but Automobile engineers may not be preferred in core mechanical jobs.
If you do not get admission in B.Tech Automobile Engineering, you may go ahead with B.Tech Mechanical Engineering. You can do M.Tech Automobile engineering after completing B.Tech Mechanical Engineering.