CHENNAI Chennai: The price of petrol and diesel in Chennai has remained almost unchanged for the last 247 days. Accordingly, a litre of petrol costs Rs 100.80 and a litre of diesel costs Rs 92.39 in the city today. Oil companies use the current crude oil price in the global market and the value of the Indian rupee against the US dollar as primary variables to determine the price of petrol and diesel on a day-to-day basis.