AbstractThis paper deals with the application of continuous thermodynamics to light and heavy oil systems using the Peng‐ Robinson equation of state. The composition of the high molar mass components in a reservoir oil is described by a continuous distribution function of some characterizing quantity, e.g. molar mass or boiling temperature. Numerical Gaussian quadrature methods are used to generate pseudo‐components and their mole fractions from distribution data. Several examples are presented for phase equilibria of solvent/crude oil systems. The results showed that semi‐infinite distribution functions, such as the Γ function, cannot be applied to all cases, e.g. dew point calculations. The Gauss‐ Legendre quadrature method coupled with spline fitting worked best for heavy oil