Oil companies yet again hiked petrol prices by Rs 1.80 per litre with effect from midnight tonight. After today's increase, petrol in Delhi will cost Rs 68.64 a litre.The rates will vary in other cities according to local levies.This is the second hike in petrol prices in less than two months and it came on a day when the food inflation rose dangerously to 12.21 per cent for the week ended October 22. The government had in June last year deregulated or freed petrol from all price controls but the retail rates have not moved in line with cost as high inflation rate forced the oil companies to seek 'advice' from parent oil ministry before revising rates.