New experimental densities in the compressed liquid state are reported for pentaerythritol tetrapentanoate (PEC5) over the temperature range of 278.15-353.15 K and for pressures up to 45 MPa. Density values (99 experimental data) have been measured with a high-pressure vibrating tube densimeter. A correction factor that was due to the viscosity of the sample was applied to the experimental density values. These data were used to determine isothermal compressibilities, isobaric thermal expansion coefficients, and internal pressures for this compound. Furthermore, the density data corresponding to the homologous series: dialkyl sebacates, 1, 10-decanediol diesters, triglycerides, trimethyolethane triesters, pentaerythritol tetraesters, and linear oligomer esters of poly(hexamethylene sebacate) were predicted using the Sako-Wu-Prausnitz (SWP) equation of state (EoS), which is linked to the group contribution approach of Elvassore et al. [Ind. Eng. Chem. Res. 1999, 38, 2110] and compared with experimental data in the literature. In addition, other two EoS-the Soave-Redlich-Kwong (SRK) and Peng-Robinson (PR) equations-were used to predict the densities of some pentaerythritol tetraesters, for which the critical constants and acentric factors have been published in the literature.