To provide a mechanical element showing wear resistance and a low coefficient of friction even under extreme pressure.

The mechanical element comprises at least two surfaces movable at peripheral speed differed from each other and a lubricant composition disposed between the two surfaces, and at least one surface of the two surfaces has an organic residue having a carboxy group, a sulfoxy group, a cyclic or non-cyclic carbamoyl group, a cyclic or non-cyclic ureylene group, a cyclic or non-cyclic sulfamoyl group or a cyclic or non-cyclic amidino group, and the above lubricant compositions comprises a discotic compound having at least one tautomeric group represented by formula (1) (wherein A is a ring constituted of 5-7 atoms and at least one atom constituting the ring may have a substituent or may condense with other ring).