New Delhi, Sep 30 : Auto fuel petrol and diesel prices rose simultaneously after a day's break on Thursday amidst volatility in global oil prices with benchmark crude remaining at a high level of $78 a barrel. Accordingly, diesel prices increased by 30 paise per litre in the national capital to Rs 89.87 per litre on Thursday while petrol prices increased by 25 paise per litre to Rs 101.64 a litre, according to Indian Oil Corporation, country's largest fuel retailer. Diesel prices have now increased for five days in the last one week taking up its retail price by Rs 1.25 paise per litre in Delhi. Diesel prices were raised on Friday by 20 paise per litre and again 25 paise per litre each on Sunday, Monday and Tuesday. Petrol prices had maintained stability since September 5 but oil companies finally raised its pump prices this week given a spurt in the product prices lately. The OMCs had preferred to maintain wait and watch policy on global oil situation before making any revision in prices. This is the reason why petrol prices were not revised for the last three weeks. But extreme volatility in global oil price movement has now pushed OMCs to effect the increase. The wait and watch plan of OMCs had come to the relief of consumers earlier as no revision came during a period when crude prices were on the rise over shortfall in US production and inventories and a pick up in demand. This would have necessitated an increase of Rs 1 in price of petrol and diesel. In Mumbai, the petrol price increased by 21 paise per litre to Rs 107.73 per litre while diesel rates increased to about Rs 97.50 a litre. Across the country as well petrol and diesel prices increased between 20-30 paisa per litre but their retail rates varied depending on the level of local taxes in the state. Fuel prices in the country have been hovering at record levels on account of 41 increases in its retail rates since April this year. It fell on few occasions but largely remained stable. After rising over three year high level of $80 a barrel earlier this week, global benchmark has now come down to $78 a barrel. Oil rates are up two per cent for the week and this is the fifth weekly gain. Since September 5, when both petrol and diesel prices were revised, the price of petrol and diesel in the international market is higher by around $6-7 per barrel as compared to average prices during August. Under the pricing formula adopted by oil companies, rates of petrol and diesel are to be reviewed and revised by them on a daily basis. The new prices becomes effective from morning at 6 a.m. The daily review and revision of prices is based on the average price of benchmark fuel in the international market in the preceding 15-days, and foreign exchange rates. But, the fluctuations in global oil prices have prevented OMCs to follow this formula in totality and revisions are now being made with longer gaps. This has also prevented companies from increasing fuel prices whenever there is a mismatch between globally arrived price and pump price of fuel. /IANS