When examined for a rough surface, the results almost follow similar trends as that for the smooth surfaces. The results for Gunmetal–Steel contact with saw tooth surface texture pattern lubricated with ionic liquids is shown in รูปที่ 6. The difference lies in the increased values of contact pressure due to the surface roughness. A clear indication of pressure perturbation due to the [C4C1 im] TF2N lubricated contact has the lowest to the order of 0.685 under similar operating conditions. The non-dimensional minimum film thickness is lowest for [C4C1 im]TF2N with a magnitude of 0.125 and the highest magnitude is observed for [C8C1 im]PF6 to the order of 0.999. Similar compound specific performance of ionic liquids is observed where the compounds of TF2N have reported increase in pressure with increase of viscosity. However the PF6 compounds along with BF4 reported decrease in contact pressure with increase of viscosity owing to the pressure effect on viscosity and density of the lubricant. The film thickness however decreased consistently with the decrease in viscosity.