AbstractThe purpose of this investigation is to understand the role of KMnO4as an oxidant additive on the lubrication properties of a soft metal + graphite composite system, under flat contact sliding conditions where the sliding surfaces interact less with the atmosphere. The sliding tests were made using a ring‐on‐disk machine, lubricated with Pb or Ag + graphite composite containing different amounts of KMnO4additive.The results showed that the addition of KMnO4in the composites reduced the friction in air up to temperatures of 500°C. The coefficient of friction was as low as 0.1. This is probably due to the fact that KMnO4decomposed during sliding to generate oxygen, which is effective in improving the lubricating ability of graphite. The optimum concentration of KMnO4in the solid lubricants (graphite + KMnO4) was 5–10 vol.%. After decomposition of all oxidant additive in the composite, the coefficient of friction of the composites, however, rose to 0