Liquid–vapor and fluid–waxy solid phase transitions were measured under pressure on a pseudo binary system made up of methane+a waxy distribution of normal paraffins ranging from C13 to C22. The composition of the paraffins in the waxy fraction was defined in order to obtain an average molecular weight equal to that of pure heptadecane. Measurements were carried out up to 90MPa by using a synthetic method on various mixtures ranging from 0 to 99% of methane. Results were compared to the phase equilibrium data of the binary system methane+heptadecane in the same conditions.