New Delhi: From next April, all car manufacturers will be required to conduct fuel-efficiency and mileage tests for new vehicle models in two conditions: with the air conditioning system on and with it off, according to a notification issued by the road transport ministry on Sunday.TOI has learned that for existing models, manufacturers may be given a few additional months to comply with the new testing requirements.The move aims to provide more realistic and accurate mileage figures to customers, thereby improving transparency, helping buyers make better purchasing decisions. The testing criteria will be applicable to both internal combustion engine (ICE) vehicles and electric vehicles (EVs). Currently, car manufacturers in India declare fuel-efficiency figures based on tests conducted with the AC system off.Earlier, the ministry had proposed to implement the new testing regime from October this year. However, after consultation with the automobile industry, revised timelines for the new models have now been notified. Industry insiders said manufacturers have asked for additional time for existing models, and timelines for those vehicles are expected to be announced soon.After conducting the test, car manufacturers and importers will have to provide details of mileage with AC on and without AC in the vehicles’ user manual and on their website.Carmakers were citing European norms where only mileage without AC is taken into account, but Indian conditions are different and this has prompted the government to bring in new norms.