The purpose of this work was to develop a method for predicting temperature dependent viscosities of biodiesel based on fatty acid ester composition. The Grunberg-Nissan equation combined with a group contribution method was used as the mixing rule to calculate viscosities of mixtures of fatty acid esters. Prediction errors at 25 degrees C were less than 2.5% for 22 mixtures of fatty acid ethyl esters. Compared with experimentally measured viscosities at 20-100 degrees C, predicted viscosities of soybean oil and yellow grease methyl esters were within 3%. For coconut, palm and canola oil methyl esters, maximum errors were underestimations at approximately 7%. (C) 2008 Elsevier Ltd. All rights reserved.