The effects of phenolic antioxidants on the adsorption of the antiwear additive, dilinoleic acid, from dodecane onto metal surfaces have been measured. The adsorbents were the metals of the Lucas piston pump used in aviation fuel systems, viz cadmium, a tool steel and an aluminum bronze. For the latter two metals particularly, adsorption at 80°C and 100°C was enhanced by the presence of antioxidants. This is attributed to a reduction in the formation of solvent oxidation products which would otherwise compete for surface sites on the metals. Comparison of results at 150°C in air and under nitrogen support this interpretation. The role of the metal surface is discused both in terms of the nature of the adsorption sites and catalysis of reactions occurring in solution.