The ongoing transition from fossil fuels to biofuels and e-fuels presents a unique opportunity to improve performance and reduce emissions . However, the chemical space of potential fuels is enormous, so achieving this goal requires procedures that can accurately predict the properties of fuels before they are synthesized. Since real fuels are typically mixtures, mixing rules are necessary that can estimate the properties of mixtures from the properties of their individual components. This paper tests some simple mixing rules for mass density and sooting tendency of diesel fuel mixtures.