This work describes and demonstrates a suite of techniques for the non-destructive examination of surface films formed from oil additives. X-Ray diffraction, reflectivity and fluorescence have been used in grazing-incidence geometry to provide information on the thickness, roughness, density, structure and composition of the layers that compose reaction films. The lubricating oils were not rinsed off the surfaces of the samples before analysis. Films were formed from neat polyalphaolefin (PAO) oil and PAO with chloroform, dimethyl disulfide, or zinc or molybdenum dialkyl dithiophosphate additive. A thick layer of crystalline FeO formed during wear lubricated by neat PAO. (C) 2003 Elsevier B.V. All rights reserved.