Heavy crude oil from the Mukhaizna oil field in Oman was emulsified with water in an attempt to decrease its viscosity. The oil has a kinematic viscosity of 7160 mm(2)/s at 30 degrees C, density of 0.9571 g/cm(3) at 15 degrees C, and asphaltene content of 4.7 wt %. The effects of changes in water content (20-30 wt %), type and concentration of surfactant, addition of a water-soluble polymer, and agitation temperatures (25 and 42 degrees C) were studied in order to identify the optimum viscosity and stability for transporting the oil. The stability was measured by the water separation rate from the emulsion. For the Mukhaizna heavy crude oil, 21-22 wt % of water content and 0.4 wt % of nonylphenol ether type or higher alcohol alkylene oxide type surfactant were found to be optimum for a stable emulsion with a concomitant significant decrease in viscosity to about (1)/(3)-(1)/(4) that of the original crude oil. This improves the transportability of the heavy crude oil and makes it suitable for use as a power generation fuel.