In today's competitive world, vehicle with light weighting is the most focused area. Vehicle light weighting can be done either by using light weight materials or by reducing the size of the existing components. In present paper later approach of vehicle light weighting is followed. It will help in design lay outing and reduce weight will add benefit to Fuel Efficiency (FE) too.Scope for light weighting is identified in exhaust system where muffler volume is optimized using Computational Fluid Dynamics (CFD) commercial tool FLUENT™. The back pressure, exhaust gas temperature, sound noise level & sound quality are chosen as design verification parameters. The muffler volume is reduced by 14.1%; resultant system become 14.1% compact with 2% lighter weight.Initially CFD analysis is performed on existing muffler and correlated with available test results. Accordingly parameters like pressure drop and flow induced noise are set as target values for new design.Same CFD analysis process is used to find the optimum solution among the series of options available. Optimized design took the shape of proto sample and test results found very well correlation between CFD and physical test results.