The automotive industry has to accommodate regulatory norms as well as customer demands in its vehicle design. These include better crash safety, new subsystems (for comfort) and high performance powertrains, all of which lead to increase in vehicle mass. Heavy vehicles consume more fuel and produce more emissions. While there are several ways to increase fuel efficiency (i.e. improving engine and transmission efficiency, reducing aerodynamic drag, and rolling resistance), the most effective means of achieving improved fuel efficiency is by reducing the overall weight of the vehicle. Hence, materials selection plays a significant role in the fuel economy, emissions as well as economics of transportation.If mass of a component is reduced there will be secondary mass reductions in other components, thus resulting in further reduction of final vehicle mass (‘mass decompounding’). The paper highlights potential benefits of using lightweight materials for vehicle body applications. An analysis was carried out to estimate life cycle energy consumption and CO2 emissions for a car wherein steel is replaced by aluminium for car body, using Indian Driving Cycle (IDC). Energy consumption at various stages, viz. raw material extraction, manufacturing, assembly and use phase are included. The analysis compares two scenarios: (a) primary weight savings without ‘mass decompounding’; and (b) considering both primary and secondary weight savings (mass decompounding), by redesigning a few sub-systems. A comparative savings in terms of energy consumption and reduction in CO2 emissions was estimated for both the scenarios. An Indian mid size sedan was chosen for analysis purpose.