The rising Lithuanian economy has the impact on the increase of the number of diesel engines which drive transport means. The fuel consumption of tractor's diesel engine is often estimated according to such parameters as certificate data about comparative effective fuel consumption and effective coefficient of efficiency when tractor operates in the mode of nominal power. However, such an estimation is not exact and comprehensive when describing the exploitation conditions. In order to characterize tractor's diesel engine one must have exact data about its long - term exploitation in uneconomical and auxiliary modes with different loads. Those reasons caused the need to carry out research of the few tractors which were exploited mostly exploitable in Lithuania.