The calorific values of petrol and CNG are 45000 kJ/kg and 50,000 kJ/kg, respectively. If you have vehicle which can run on petrol as well as CNG, which fuel will you prefer and why?

I would prefer a vehicle that runs on CNG. CNG has a higher calorific value, meaning – the amount of heat released when 1Kg of a substance is burned. So, its efficiency is also high when compared to that of petrol. Moreover, CNG is also economic and produces lesser harmful products.