The phase behavior of refrigerant with lubricant oil is an important issue for designing the refrigeration system. R1234ze(E) was proposed as a possible replacement for R134a recently. In this work, the p-T-x data of R1234ze(E) with pentaerythritol tetrahexanoate (PEC6) and pentaerythritol tetraoctanoate (PEC8) were obtained based on the isochoric method at temperatures ranging from 283.15 to 353.15 K. The experimental data were correlated by Peng-Robinson equation of state with HVOS mixing rule in which the excess Gibbs energy at infinite pressure was represented by Wilson equation. The absolute average deviation and maximum deviation of the pressure from the calculated values was 0.79% and 2.67% for R1234ze(E)+PEC6 system, respectively. For R1234ze(E) +PEC8 system, the absolute average deviation and maximum deviation of pressure were 0.98% and 2.89%. (C) 2015 Elsevier B.V. All rights reserved.