The present study focuses on the determination of the equilibrium solubility (C*), volumetric liquid-side mass transfer coefficient, (kLa), for 5 different gas (CO, H2, CO2 and N2, He that can be used as surrogates of CO and H2 respectively) in a Fischer-Tropsch liquid (polyalphaolefins) that can be used for reactor start-up. The data are obtained in a 4 Liters Zipper-Clave stirred tank reactor operating in a gas inducing mode within wide range of operating conditions covering those of the industrial Fischer-Tropsch synthesis process. The effects of operating variables, including pressure (6-30 bar) and temperature (300-500K) on kLa and C* values were studied. The transient physical gas absorption technique was used to determine kLa.