Asphaltene instability is an important problem in flow assurance, especially for wells and for the particular case of commingled production that can lead to oil incompatibility. It is, therefore, important to assess the probability of asphaltene deposition in the first stages of field development. Toward this end, several correlations have been proposed, such as the Asphaltene Stability Index and the deBoer plot. More detailed models have been proposed that are able to estimate the range of pressures at which asphaltene deposits are expected. Among these models, one of the most popular approaches is based on the concept of the solubility parameter, as it is believed that the quality of the solvent is a critical parameter in the stability of asphaltenes in oil. These models have successfully been used to estimate the onset of asphaltene deposition in field conditions. The models use the oil and asphaltene solubility parameters. Their values are simultaneously estimated by means of onset flocculation experiments. The problem that arises is that these two parameters are interconnected in the equations of the model. It is believed that, with an independent estimation of one of the two parameters, the determination of asphaltene instability in the PT diagram would be more reliable. This work presents correlations of the oil solubility parameter with density and viscosity. With this procedure, the solubility parameters of oil and asphaltenes are estimated independently. The correlations presented in this work allow the estimation of the dependence of the solubility parameter on temperature in the temperature range of interest. In addition, because density and viscosity are readily available in the PVT report, the load of experimental work in the laboratory can be significantly reduced.