This paper discusses the role surface analytical science has
played in understanding the complex phenomena occurring during lubrication
of modern internal combustion engines. The interactions between the
multi-functional lubricant additives and the various metallic surfaces
present in the tribological contacts are complex and lead to the formation
of inhomogenous multi-layer protective surface films. Surface analysis by
ultra-high vacuum (UHV) techniques such as x-ray photoelectron
spectroscopy, Auger electron spectroscopy and secondary ion mass
spectrometry has allowed model structures for these films to be derived
through which the behaviour of the contact can be understood. Non-UHV
probes have elucidated the role played by the soluble, partly reacted or
degraded film precursors that occupy the interfacial region between the
solid surface and the liquid lubricant, and have allowed the mechanical
properties of the films to be investigated on a micro- and nano-scale. The
use of surface analytical techniques to study interactions between
lubricant species and combustion soot is also discussed.