Abstract For some offshore fields, multiphase production and transport can be an economic solution. In the case of waxy crude reservoirs, keeping the light ends in contact with the stock tank oil can reduce the onset crystallization temperature. The influence of light components and ends on the wax appearance temperature (WAT) of two oils has been studied by differential scanning calorimetry. In order to determine the role of the pressure, an equipment based on the use of an ultrasonic pulse has been designed. The main features of this device are presented. It has been found that light components induce a decrease of the onset crystallization temperature of waxy crudes. This decrease is proportional to the amount of light ends, inversely proportional to their carbon atoms number, and dependent on the chemical nature of the components added. Furthermore, it has been possible to correlate these experimental data, in order to calculate the variation of the wax appearance temperature of two stock tank oils, due to the addition of a light end.