Instead of PG Diploma, considering future demand of Mechanical Engineers and career prospects, I would perhaps advise you to pursue an Associate Degree Equivalent to Btech in Mechanical Engineering from Institution of Engineers, Kolkata. After this AMIE Certification, you may pursue MTech from some of the Good Goverment, State or Private Engineering Institutions in West Bengal, followed by a strong career in the Mechanical and Industrial Engineering Industry.

For more information about Institution of Engineers, Kolkata do follow the link below

https://www.careers360.com/colleges/the-institutions-of-engineers-india-kolkata