Oily sludge is one of the hazardous materials if not properly treated. Thus, recovering oil from oily sludge could reduce environmental problems and have substantial commercial benefits. However, prior to oil recovery, dehydration is extremely necessary to effectively reduce energy consumption. Fry-drying is a novel dehydration method which characterized by low energy consumption and high drying efficiency. In this study, the spent lubricating oil of vehicle was used as frying medium, which enabled a drying operation that was environmental friendly and economically competitive. A modified Dean-Stark apparatus-II was designed to accurately and efficiently measure the water and oil contents of the fried sample. Considering the oil adsorption mechanism that occurred during the fry-drying of oily sludge, a suitable equation for the forced convective heat transfer coefficient (h) was established using the fundamental of energy balance. Results showed that the h change tendency and the calculated maximum value were distinct from previous food frying findings. Finally, the entire fry-drying process of oily sludge was divided into four periods according to the different sample drying rate change tendencies. The heat and mass transfer processes of each period were also analyzed. (C) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.