To keep the environment clean, the government has introduced Euro-4 petrol and diesel in 13 cities, including Delhi on Thursday. Launching the Euro-4 in the national capital, the Chairman of Environment Pollution Control Authority, Mr. Bhurelal said that to minimise the air pollution level, the government has made it mandatory to have the Euro-4 system in all the vehicles which will be sold from Thursday. He said that refineries are spending three rupees per litre for making Euro-4 diesel and petrol, while they have increased only 50 paise for the customers. Mr. Bhurelal said that Grade-3 Euro system will be made mandatory for other cities within a month.