2.2. Experimental results and discussion
Fig. 2 shows a log–log plot of the measured friction coefficient as a function of the product of the viscosity η and the entrainment speed U, where the entrainment speed is here equal to one half of
the sliding speed, U ¼ V =2. The results corresponding to a fixed load are denoted by markers of the same colour, and the results corresponding to a fixed lubricant are denoted by markers of the same shape, see the legend in Fig. 2.