NOVELTY - Pyrolysis oil comprises fuel free of emulsifiers, where the fuel is an emulsion of (a) at least one mineral oil and/or synthetic oil and/or natural oil in (b) a pyrolysis oil in a ratio of (a):(b), in wt.% of 1-15:99-85, optionally containing a lubricant, where the Sauter mean diameter (SMD) D32 of droplets of (a) in the emulsion is 1-15 mu m.    USE - The pyrolysis oil is useful for operating the internal combustion engine (claimed).    ADVANTAGE - The pyrolysis oil can be obtained at lower cost, since it is free of emulsifiers, with improved ignition and lubrication properties.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) preparing the pyrolysis oil containing fuel comprising: providing a mixture of (a) and (b); and treating the mixture with a homogenizer (4) to form the emulsion, so that the SMD D32 of droplets of (a) in the emulsion is 1-15 mu m;    (2) an internal combustion engine system comprising: a reservoir (1) for pyrolysis oil; a reservoir (2) for the mixture of (a) and (b); the homogenizer configured to provide the emulsion, including an inlet connected with the reservoirs and an outlet; and at least one internal combustion engine (5) including at least one combustion chamber, where the homogenizer is connected with the internal combustion engine for operating the same by burning the emulsion; and    (3) operating the internal combustion engine system comprising: providing the internal combustion engine; providing the homogenizer; introducing (a), (b) and optionally a lubricant into the homogenizer; operating the homogenizer to provide the emulsion of (a), (b) and the lubricant; and burning the injected emulsion within the combustion chamber.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic block diagram of the internal combustion engine system.    Reservoir for pyrolysis oil (1)    Reservoir for the mixture of oils (2)    Reservoir for the lubricant (3)    Homogenizer (4)    Internal combustion engine (5)