The properties of finished fuels are crucial to the optimization of not only engine operation, but also for the processing of fuels. As petrochemical feed stocks become increasingly scarce, the interest in renewable feed stocks grows. However, there are many challenges to be overcome before renewable fuels (biofuels) can be used to extend or enhance the supply of petroleum based fuels. The composition explicit distillation curve method, developed at NIST, provides a unique approach to join fuel composition with the thermophysical properties. Of critical importance is the moiety family breakdown of a fuel, relative to a mathematical description such as an equation-of-state. We are using a new 600 MHz NMR, equipped with a cryogenic probe and diffusion accessory to develop an advanced approach to understanding the moiety family breakdown. The high resolution and sensitivity provided by this instrument allows unparalleled details to emerge. For example, some mixtures of gasoline and biodiesel fuel have unique properties that can only be studied through a separation method (i.e., distillation) because the suite of chemical compounds present is so diverse. The NMR measurement is proving to be critical to these efforts since it provides guidance in developing the appropriate surrogate mixtures for modeling and does so relative to the thermodynamic behavior provided by distillation. The integration of this experimental approach with fluid theory relates this composition to thermodynamics and will further both the measurement capability and modeling capability.