The paper describes tests to determine whether two methods of surface hardening, sulfinuz and tufftride, improved the lubricated wear properties of a crank-shaft steel. Very pure hexadecane was used as lubricant in a modified ball and triplane test machine. The surprising result was that wear rate increased logarithmically with actual contact temperature up to 160°C when it dropped two orders of magnitude. Below 160°C, the wear debris was red ferric oxide Fe203,· beyond 160°C it changed to the much softer magnetite Fe304. Approximate figures for the energy of the two (mild) wear processes were obtained, 12–15k cal/g mole for Fe203and ˜25k cal/g mole for Fe304. No explanation for the 160°C transition, which was independent of speed and contact pressure, could be found.