Recently, biodiesel is receiving global attention as an alternative fuel for diesel engines because of its many advantages compared to petroleum-based diesel fuel. Despite many advantages, it has also some drawbacks such as: poor flow characteristics, lower energy content, higher price and viscosity. Higher viscosity leading poor atomization with larger droplet size results in bad mixing quality and incomplete combustion. Blending of biodiesel with diesel or alcohol is one of the most appropriate techniques to overcome high viscosity problem. Although viscosity data of biodiesel-diesel fuel binary blends at different temperatures are abundantly available in the literature, these of ethyl ester-diesel-alcohol ternary blends including especially higher alcohols are still insufficient. Therefore, in this study, waste cooking oil ethyl ester (biodiesel) was produced by means of transesterification, and it was blended with diesel fuel and different alcohols (methanol, ethanol, isopropanol, n-butanol and n-pentanol). Viscosities of the prepared ternary blends were measured at different temperatures accordingly DIN 53015. Finally, a rational model depending on blend temperature or alcohol fraction was proposed for estimating viscosities of them, and it was tested with the well-known other models (Arrhenius, Kendall-Monroe, Andrade and Vogel) for its predictive ability. (C) 2018 Elsevier Ltd. All rights reserved.