Abstract
Commercial oil fortifier was added to fully‐formulated crankcase oils, and their performance, in terms of friction, wear and, most importantly, the role of the additive protective layer on the sliding surfaces, was investigated. Tests were performed on a pin‐on‐disc machine using steel and steel sliding partners under boundary lubrication conditions. Tests were carried out at a constant load and velocity at different temperatures with different lubricants and the results were achieved using analytical methods such as light microscopy, electron microscopy and X‐ray diffraction. Related to the experimental work, lubricants and the lubricants containing oil fortifier presented satisfactory protective additive layers which were identified on the wear track at high and low temperatures.