The densities and speeds of sound of four surrogate diesel fuels of varying compositional accuracy were measured at atmospheric pressure over the combined temperature range 278.15-343.15 K. Measurement results for the surrogate fuels were compared to results obtained for the target fuel as well as to predicted values. For both density and sound speed, the least compositionally accurate four-component surrogate was the most dissimilar to the target fuel, with average absolute deviations (AADs) of 3.3 and 2.1%, respectively, while the most compositionally accurate nine component surrogate was the most similar, with AADs of 0.8 and 0.4%, respectively. However, the relative behavior of the other two surrogates implies that greater complexity is not always required in a surrogate; the minimal number of components required for a given surrogate fuel will ultimately be determined by the specific research goals it is meant to achieve.