Complete recycling of waste edible oil has recently attracted considerable attention as a worldwide social problem. Production of a biodiesel fuel from used vegetable oil is considered an important step in reducing and recycling waste oil. This technology employs used vegetable oil as a potential renewable alternative resource to fossil diesel fuel, and the transesterification reaction is the usual process to obtain biodiesel. The objective of this work is to study the transesterification of waste oil with methanol in the presence of several Y-type zeolites with different Al2O3 content. In this study, the reaction is carried out in a continuous tubular steel reactor using zeolite Y as catalyst, being tested at atmospheric pressure within a reactor temperature range of 200-476 degrees C and methanol/oil molar ratio of 6. The results show an important decrease of viscosity of the product obtained until values close to biodiesel specifications.