Three novel S-P-N type triazine derivatives were synthesised, and their structures were analysed through elemental analysis, and their tribological behaviours as additives in rapeseed oil were evaluated using a four-ball tester. The extreme pressure and antiwear (AW) mechanism was investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The results indicate that the additives possess excellent load-carrying capacity and AW ability but have some friction-reducing property only under the low load condition. Based on the results of XPS and SEM analysis, it can be seen that tribochemical reaction occurred between the synthesised compounds and metal surfaces during the sliding process, to form a complex film which has excellent load-carrying capacity and AW ability. Copyright © 2010 John Wiley & Sons, Ltd.