Abstract: The present invention provides a method of upgrading mixed waste plastic pyrolysis oil comprising the steps of providing a pyrolysis oil stream derived from mixed waste plastic, subjecting the pyrolysis oil stream to fractional condensation to obtain three pyrolysis oil fractions, determining properties of the pyrolysis oil fractions, determining an adjusted proportion of the pyrolysis oil fractions to be fed to a hydro-upgrading section for obtaining a product with a predetermined product specification, feeding the pyrolysis oil fractions in the adjusted proportion to a pyrolysis oil hydro-upgrading section to perform a hydro-upgrading operation, adjusting one or more control parameters of the pyrolysis oil hydro-upgrading section according to the adjusted proportion of the pyrolysis oil fractions and the predetermined product specification; and separating an hydro-upgrading section outlet stream to obtain a product stream with the predetermined product specification.