Obstructed fuel lines and filters in diesel engines during cold weather is a common phenomenon today. It is the perception of the marketplace that water crystallization is a contributor to such blockage. However, demonstrating this effect in the laboratory has been a problem.Standard testing methods - such as pour point (ASTM D-97), cloud point (ASTM D-2500), and cold filter plugging point (IP-309/75) - were not designed as and do not provide a sensitive means to measure the performance of deicing products. In fact, all of the aforementioned tests are derivative measures of fuel icing. A more direct measure of the temperature of ice formation in the fuel delivery system is required.Although lower alcohols - such as methanol, ethanol, or 2- propanol - have been recommended for use in combination with other diesel fuel additives, diesel engine manufacturers place strict limits on the maximum levels allowed for warranty purposes. To provide superior deicing performance without the use of these alcohols, candidates were evaluated using differential scanning calorimetry (DSC) data. DSC was successfully used to measure the freezing point of water removed from a dosed diesel fuel and to select the most effective deicing additive.