This Technical Report describes the key properties of fast pyrolysis bio-oils and their importance to the fuel quality for use in stationary internal combustion engines. Internal combustion engine (ICE) in the scope of this document means a type of engine in which heat energy and mechanical energy is produced inside the engine. ICE include compression ignition engines (diesel engines) and gas turbines. Attention is drawn to differences especially in those properties, which can have an effect on the required engine performance, such as ash, acidity, viscosity, combustion properties, and sulfur content. In addition to the quality requirements and related test methods for FPBO, further instructions on storage (Annex A), sampling (Clause 4), and materials compatibility (Annex B) are given. NOTE For the purposes of this Technical Report, the terms % (m/m) and % (V/V) are used to represent the mass fraction (¼) and the volume fraction (Æ) of a material, respectively.