Adulteration of fuel at petrol bunks in the city is on the rise. At least 1,075 cases have been registered this year against various oil companies as against 931 cases last year. According to legal metrology department, at least 299 cases have been booked against HPCL, 531 against IOC, 188 against BPCL and 17 against Reliance in 2007-08. Receipts with oil companies showed a fall in total revenues from sales of diesel and petrol despite the increase in sale of vehicles, the officials said. They attributed the discrepancy to adulteration of fuel at petrol bunks.