A method is disclosed for preparing fuel components from waste pyrolysis oil. Exemplary embodiments include providing a waste pyrolysis oil having plastic pyrolysis oil and/or tyre pyrolysis oil, and impurities; purifying the waste pyrolysis oil by hydrothermal treatment with water or alkaline water; separating the hydrothermally treated waste pyrolysis oil from an aqueous phase; preparing a hydroprocessing feed from the hydrothermally treated waste pyrolysis oil; hydroprocessing the hydroprocessing feed catalytically with hydrogen to cause hydrogenation; and recovering a hydrocarbon fraction boiling in a liquid fuel range.