Fuel efficiency standards for vehicles directly influence mileage and carbon emissions per litre of fuel burnt and are one of the most difficult and least understood policy instruments in India. We need to develop a better understanding of them if we are to achieve multiple objectives of reducing oil demand and emissions of heat-trapping gases, protecting consumers from rising oil prices, strengthening energy security, driving technological innovation, and catalyzing electrification of the vehicle fleet. Even though India has taken steps to substantially improve its mass emissions standards for vehicles to Bharat Stage VI (BS-VI) in 2020 (that regulates emissions of toxic pollutants), regulatory mandate and standards for reducing energy and carbon footprints of vehicles has remained weak. This is a matter of serious concern as vehicle numbers and freight transport are growing rapidly, leading to an exponential rise in fuel consumption.