The usage of rapeseed oil as a fuel for agricultural machinery was demonstrated successfully in the last years. Along with rapeseed oil, the suitability of other vegetable oils to be used as fuel is discussed. For fatty acid methyl esters the influence of the fatty acid composition and of structure indices on fuel properties and the operation and emission behaviour of engines was already researched, but not for vegetable oils. Hence, target of the paper was to identify structure indices of vegetable oils and to research, if they can be related to important fuel properties and the ignition, combustion and emission behaviour. The ignition and combustion behaviour was studied using a constant volume combustion chamber device and the emission behaviour was researched using two vegetable oil compatible tractors.