WARNING: This page is about a different car, the 2014 Mitsubishi Outlander. However, it is still accessible from the selected car via links, so may be relevant.
Using special tool MB991398, tighten the spark plug to the specified torque.
Tightening torque: 18 ± 2 N.m (13 ± 1 ft-lb)
Fig 1: Identifying Spark Plug And Special Tool MB991398