NEW DELHI: Starting next April, all car manufacturers will be required to perform fuel-efficiency and mileage tests for new vehicle models under two conditions: with the air-conditioning system turned on and with it turned off, according to a notification issued by the road transport ministry on Sunday.For existing models, manufacturers may be granted a few additional months to comply with the new testing requirements, TOI has learnt.The move is aimed at providing customers with more realistic and accurate mileage figures, which will improve transparency, helping buyers make better-informed purchasing decisions. The testing norms will apply to both internal combustion engine (ICE) vehicles and electric vehicles (EVs). At present, car manufacturers in India declare fuel-efficiency figures based on tests conducted with the AC system switched off.Earlier, the ministry had proposed implementing the new testing regime from Oct this year. However, following consultations with the automobile industry, the revised timeline for new models has now been notified. Industry insiders said manufacturers have sought additional time for existing models, and the timeline for those vehicles is expected to be announced soon.After carrying out tests, car manufacturers and importers will be required to put the mileage for with and without AC switched on in the user manual of vehicles and on their website as well.Car manufacturers were citing European norms where only mileage without AC is taken into account, but Indian conditions are different and this has prompted govt to come up with the new norms.