This paper presents the impact of essential oils on the lubricity of automotive diesel. Nine essential oils were used as lubricating additives on two low sulfur diesel fuels, at the concentration range of 2005000 ppm. Tribological experiments carried out on the high frequency reciprocating rig showed that five of nine essential oils used provide satisfactory mean wear scar diameter (WS 1.4) of less than 460 mu m, at the concentration levels of 200-5000 ppm. Among the essential oils, those having the higher density and viscosity appeared to have better lubrication performance, exhibiting smaller wear scar diameter (WS 1.4) than the limit of 460 mu m. Overall, the five essential oils seem to be better lubricants than others, maybe due to their chemical structure characteristics. (C) 2008 Elsevier Ltd. All rights reserved.