Abstract Saponified, palm, olive, rapeseed and castor oils were pyrolysed (at 750 °C for 20 s) by pyrolysis gas chromatography with mass selective and flame ionisation detection (Py-GC/MSD and FID) to clarify their thermochemical behaviours. The liquefiable compounds recovered from palm, olive and rapeseed oils mainly contained linear alkenes (up to C 19 ) and alkanes (up to C 17 ), both similar to those found in gasoline (C 4 –C 10 ) and diesel fuel (C 11 –C 22 ) boiling range fractions of petroleum, whereas in the case of castor oil a significant amount of undesired oxygen-containing products (e.g., ketones and phenols) were formed. The obtained data on reaction mechanisms can also be utilised in applications where various biofuels are produced, for example, from the extractive-derived by-product (tall oil) of kraft pulping.