My placement is in December 2k17 !
Since I am a part of placement Team at IITB, let me tell you about Placement of IITB Mech-Design !
Placement of all IIT starts from Dec 1. Within first four days, all design students were placed in core companies.
As far as salary is concerned, it depends on a company. On an average, one can expect 9LPA if he/she has enough enthu in core companies. For non-core, there is no limit for package (then it comes down to sector i.e. Finance, Consulting, Analytics).
PS : I am more of non-core guy ! ( somehow I figured it out after coming to IITB).