Some engine oil additives and their effects on antiwear film formation

Engine oils contain several additives dissolved or dispersed in a hydrocarbon oil base. Each of these additives are meant to perform one or more functions, which may or may not relate directly to friction and wear. The performance of additive mixtures, however, cannot usually be predicted in a simple fashion, such as, for example, by a rule‐of‐mixtures approach. In addition, additives which are meant to perform functions unrelated to friction and wear may impact the efficacy of friction and wear additives. Many of these effects can be explained by the study of additive interactions by various spectroscopic, colligative and other physical chemical methods. This paper presents a review of published information on that topic, with a view to stimulate further work as well as to provide insight on issues facing engine oil formulators.