Delhi will be the first city in the country to leapfrog from Euro-IV grade petrol and diesel to Euro-VI. Cities in the national capital region like Noida, Ghaziabad, Gurugram and Faridabad as well as 13 major cities including Mumbai, Chennai, Bengaluru, Hyderabad and Pune will switch over to cleaner Euro-VI grade fuel from January 1 next year. Rest of the country will follow suit from April 2020.