Vegetable oils and animal fats are applicable as fuels in standard diesel engines after having adapted the fuel system for electronically controlled dual fuel regime oil/fat-fossil diesel. In this contribution, performance and emission characteristics of the engines running on rapeseed oil, lard, or chicken fat are given and compared to those of fossil diesel and fatty acid methyl esters. The results of engine tests of these fuels show a decrease in maximum power and maximum torque in comparison to fossil diesel due to a lower energy content of triacylglycerols. These values are influenced also by a type of the engine used at testing. When compared to fossil diesel, the opacity of oil/fat based fuels is higher for an engine with lower injection pressures while it is lower for an engine with higher injection pressures. The level of both controlled and uncontrolled emissions is low for all tested biofuels and is low also for the reference fossil diesel. The results of performance and emission tests for rapeseed oil containing 3 and 6 vol.% of anhydrous ethanol are comparable to those obtained for pure oil. In this paper, practical experiences based on long-term operation of adapted vehicle fleet fuelled with oil/fat-fossil diesel are mentioned. (C) 2011 Elsevier B.V. All rights reserved.