Ninety-seven vapor-phase PvTx measurements are reported for six binary blends of cis-1,2,3,3,3-pentafluoroprop-1-ene (R1225ye(Z)) and isobutane (R600a), and sixty-six vapor-phase PvTx measurements are reported for four binary blends of 3,3,3-trifluoropropene (R1243zf) and R600a. The R1225ye(Z)/R600a data were recorded for six isochores of (0.0586, 0.0633, 0.0718, 0.0902, 0.1076, and 0.1218) m(3).kg(-1) for temperatures (303 < T < 383) K for six R600a mole fractions (0.504, 0.175, 0.797, 0.345, 0.477, 0.916). The R1243zf/R600a data were recorded for four isochores of (0.0944, 0.1614, 0.2306, and 0.6145) m(3).kg(-1) for temperatures (303 < T < 383) K for four R600a mole fractions (0.225, 0.434, 0.898, 0.282). The data were fitted using three equations of state: (1) ideal gas, (2) Peng-Robinson, and (3) truncated virial.