Automotive Silencers (or) Mufflers are used to minimize the noise level and vibrations produced in the engine exhaust gas. The Mufflers usually contain complex internal components such as extended inlet and outlet tubes, thin baffles with eccentric holes, internal connecting tubes, perforated tubes, flow plugs, and sound absorbing materials. In this project, thermal analysis is carried out in the existing muffler of C.I.engine. The various influencing factors of muffler such as thermal concentration, thermal stress and properties of material have been analyzed by the software and the input values for the analysis are measured from the experimental setup. Based on the results of analysis, the optimal modification is to be done in the design in order to improve the life and performance of muffler. © 2015 Elsevier B.V., All rights reserved.