New Delhi, July 17 : Unexpected rise in diesel prices despite slower demand has extended the gain for the transport fuel over petrol in Delhi. With a 17 paise hike in diesel price in New Delhi on Friday while petrol prices remaining steady, the gap between the two auto fuels has further widened in the national capital. Last month, diesel prices overtook that of petrol in the national capital, in an unprecedented development. Diesel was priced at Rs 81.35 per litre on Friday in the capital, higher than the previous level of Rs 81.18 a litre. Petrol prices, however, remain unchanged at Rs 80.43 a litre, the same level as June 29 when it's pump price rose marginally by 5 paisa over previous days price. With this, diesel is now almost a rupee higher than petrol overturning the advantage of running a vehicle on the fuel. With the price trends in diesel, it may soon catch up with petrol prices in other metros as well. Along with the Capital, diesel prices marginally increased in other metro cities as well but there the price of transportation fuel is still between Rs 6-8 per litre lower than petrol. Oil companies began daily revision of the two auto fuels from a June 7 after keeping the price unchanged for last 82 days during Covid-19 related lockdown. Since then petrol and diesel prices have increased by Rs 9.5 -- Rs 11.5 per litre respectively. Last week petrol and diesel prices remained inched for four days before diesel prices increasing on Sunday and again on Monday. /IANS