Figure 3. Comparison of the average friction coefficients for the last 250 m of the tests presented in figure 2 for untextured polished controls and wide as well as narrow scale-like surface morphologies. In (a) for lubricated conditions with the additive-free mineral oil FVA No.1 (η(20 °C) = 28.0 mPa s) and a steel-on-steel contact. In (b) under dry sliding conditions with the textured steel pins sliding against sapphire discs.