Petrol price today crossed Rs. 100 a litre mark after rates were hiked by 80 paise a litre and 70 paise in case of diesel, taking the total increase in rates in one week to Rs. 4.80 per litre. Petrol in Delhi will now cost Rs. 100.21 per litre as against Rs. 99.41 previously while diesel rates have gone up from Rs. 90.77 per litre to Rs. 91.47, according to a price notification of state fuel retailers.