As an alternative to solvent addition to the steam-assisted gravity drainage process for bitumen recovery, coinjection of biodiesel with steam as a surfactant additive to reduce bitumen-water interfacial tension was considered. The density and viscosity of bitumen and bitumen-pentane mixtures up to 15 % pentane concentrations by mass were measured at a 1 MPa pressure and up to 448 K temperature. The interfacial tension between bitumen, bitumen-pentane mixtures up to 15 % pentane concentrations, bitumen-biodiesel mixtures up to 0.3 % and water, and process water was also measured at a 1 MPa pressure and up to 423 K temperature. Laboratory tests showed that the density of bitumen-pentane mixtures decreased linearly with an increase in pentane content, and their viscosity decreased exponentially with the increase in temperature. A decrease in bitumen viscosity with an increase in pentane content was dramatic at low temperatures and became less sensitive at temperatures above 373 K. Interfacial tension measurements suggest that asphaltic acids naturally occurring in bitumen act as surfactants. The decay in interfacial tension with time is attributed to the diffusion of surfactant species in a bitumen droplet. The increase in interfacial tension of bitumen-pentane mixtures and water with an increase in pentane content and temperature needs further attention because of its commercial application.