The effect of ionic liquids in terms of minimum film thickness is shown in รูปที่ 5(b). As a general trend the lubricants with higher viscosity results into thicker lubricating films. Keeping the operating, geometric and material parameters constant, the lubricants with higher viscosity results into thicker lubricating films. The same trend has been observed in the present study, the [C8C1 im] PF6 having highest viscosity reported thicker lubricating film and the [C4C1 im]TF2N having lowest viscosity reported thinnest lubricating film.