Shares of upstream oil companies mainly Oil & Natural Gas Corporation (ONGC) and Oil India gained up to 4 per cent on the BSE in Thursday’s intra-day trade after the government cut the windfall profit tax on domestically produced crude oil from Rs 5,050 per tonne to Rs 4,350 per tonne. The additional excise duty on aviation turbine fuel (ATF) was also cut to Rs 1.5 per litre from Rs 6 per litre earlier.