New Delhi, Sep 26 : Auto fuel prices in the country have maintained stability amid volatility in global oil prices, but the oil marketing companies on Sunday increased the pump price of diesel marginally while maintaining stability in petrol prices. Accordingly, diesel prices increased by 25 paise per litre in the national capital to Rs 89.07 per litre on Sunday while petrol price remained unchanged for the 21th consecutive day, according to Indian Oil Corporation, country's largest fuel retailer. Diesel price was raised on Friday as well by 20 paise per litre which oil marketing company sources said was based on the global price movement of the fuel. OMCs have preferred to maintain their watch prices on global oil situation before making any revision in prices. The wait and watch plan of OMCs has come to the relief of consumers as no revision has come during a period when crude prices were on the rise over a shortfall in the US production and inventories and a pick up in demand. This would have necessitated about Rs 1 increase in price of petrol and diesel. In Mumbai, the petrol price was stable at Rs 107.26 per litre while diesel rate increased to about Rs 96.68 a litre. Across the country as well petrol price remained static on Sunday while diesel price increased marginally. Fuel prices have been hovering at record levels on account of 41 increases in its retail rates since April this year. It fell on a few occasions but largely remained stable. On Sunday, global benchmark Brent crude rose over $78 a barrel. Oil rates are up 2 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 become 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 and pump price of fuel. /IANS