The mass of carbon dioxide that is released when one MJ of energy is released from fuel can be estimated to a good approximation.[50] For the chemical formula of diesel we use as an approximation C nH 2n. Note that diesel is a mixture of different molecules. As carbon has a molar mass of 12 g/mol and hydrogen (atomic!) has a molar mass of about 1 g/mol, so the fraction by weight of carbon in diesel is roughly 12/14.