The paper describes an experimental study concerning the feasibility of using bio-oil obtained from flash pyrolysis of wood for fuelling diesel power plants. The research is based on various tests aimed at verifying relevant operative characteristics of the fuel: spray analyses, engine tests, thermogravimetric analyses (TGA), single-drop reactor tests and corrosion tests. The spray analyses show that the achievement of a satisfactory atomisation with flash-pyrolysis oil is problematic. The engine experimentation shows that flash-pyrolysis oil needs to be modified or mixed (e.g. with alcohol) to make self ignition possible. Besides, unacceptable build-up of carbonaceous deposits, injection system clamping and engine seizure occur. Very large char generation is the main finding of the tests in the TGA apparatus and in the single-drop atmospheric reactor (“drop-tube”). The corrosion tests demonstrate that steel undergoes fast erosion by contact of flash-pyrolysis oil. All these findings show that characteristics of current-production flash-pyrolysis oil are not suited for its utilisation in diesel engines.