Thermal characteristics and rheological behaviour of eight crude oils covered a wide range of fluid composition and properties were studied by differential scanning calorimeter (DSC) and viscometry. Wax appearance temperatures (WAT) of crude oils were determined by DSC and viscometry. Good agreement is obtained between the results. The dynamic viscosity in the Newtonian temperature range of the crude oils (above 30 degrees C) generally obeyed a simple first-order Arrhenius type of temperature dependence. Activation energies of flow in the non-Newtonian range are not uniquely defined.