Petrol prices will go up by 50 paise a litre from midnight tonight in 13 big cities, including Delhi and Mumbai, where cleaner Euro-IV grade fuel will be supplied from tomorrow.Petrol price in Delhi will go up by 50 paise per litre to 47 rupees and 93 paisa and diesel by 26 paise to 38 rupees and 10 paise a litre on account of supply of cleaner Euro-IV fuel. AIR correspondent reports, thirteen big cities, including Delhi, Mumbai, Kolkata, Chennai, Hyderabad, Bangalore, Lucknow, Kanpur, Agra, Surat, Ahmedabad, Pune and Sholapur will move from Euro-III grade fuel to Euro-IV from tomorrow. Rates will vary from city to city depending upon local taxes.