The lower critical end point temperatures of [ethylene + comonomer + n-hexane + linear low-density polyethylene (LLDPE)] systems are shown to be strongly correlated with solvent average molecular mass and mole fraction-averaged carbon number, but not solvent density or critical temperature. A synthetic-visual method is used to measure vapor-liquid, vapor-liquid-liquid, and liquid-liquid phase boundaries for quasiquaternary (ethylene + comonomer + n-hexane + LLDPE) systems for the 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, and 1-decene comonomers, and for quasiternary (ethane/n-decane/4-methyl-1-pentene + n-hexane + LLDPE) systems. The reported data span temperatures of T = (375-465) K and pressures of P = (0.5-15) MPa. In all systems, the mass fraction of the LLDPE ((M) over bar (w) = 199 kg.mol(-1); (M) over bar (w)/(M) over barn, = 2.62; 2.56 mol % 1-hexene) was kept at 3 wt % and solvent compositions were chosen to represent conditions found in the solution polymerization process. The modified Sanchez-Lacombe equation of state can predict the quasiquaternary systems' phase behavior with moderate accuracy using parameters adjusted to quasiternary data.