We used NEMD simulations to compare the mechanochemical reactivity of TCP on three ferrous surfaces, as shown in Figure . TCP is a molecule composed of three cresyl (methylphenyl) groups linked to a phosphate group. It is produced from cresol, which naturally contains a mixture of isomers with the methyl group in the ortho-, meta-and para-positions. The ortho-isomers of TCP are known to be toxic and modern production methods have reduced the concentration of these to very low levels. Therefore, the TCPs used in current aviation lubricants generally contain mixtures of the meta-isomers and also some paraisomers. The para-isomers were shown to have poorer lubricating properties compared to mixtures of isomers. However, a recent study showed that the para-isomer is only slightly more reactive than the meta-isomer on ferrous surfaces. In this study, we chose to study pure tri-meta-cresyl phosphate for simplicity; its molecular structure is shown in Figure .