The square-well fluid thermodynamics and liquid structure derived from Barker-Henderson＇s perturbation theory, including a truncation correction, are used within a SAFT framework to develop a prototype of an engineering equation of state for alkane chains, referred to as SAFT1. For small n-alkanes, not only the vapor pressure and liquid density, but also the second virial coefficient, heat of vaporization, and heat capacity, are found to be more accurate. SAFT1 parameters are well behaved and hence easy to estimate reliably for high-molecular-weight alkanes and polyolefins. These parameters are found to predict cloud points in mixtures of homo- and heterosegmented molecules, such as polyolefins, without fitting.