Australian crude oils, which generally contain little asphaltenes, nevertheless give rise to fouling in refinery pre-heat trains. In this research, the fouling of a series of such crude oils and their blends is being assessed. The present work focuses on thermal fouling resulting from heating Gippsland crude oil at moderate temperatures. The oil is maintained under nitrogen at a pressure of 379 kPa and re-circulated at bulk temperatures of 80-120degreesC through an electrically heated annular probe at velocities in the range 0.25-0.65 m/s with surface temperatures from 180-260degreesC. Experiments are run for periods up to ninety hours at constant heat flux. Fouling is detected by the increase of wall temperature of the probe. The oil is characterized by its filterable solids content, density, and viscosity both before and after the fouling run. The trends in fouling rates are compared to predictions of the threshold-fouling model proposed by Ebert and Panchal [6]. Data on deposit composition are presented, and the fouling mechanism is discussed.