Always tighten MEG spark plugs to the engine manufacturer's tightening torque. If this information is not available, screw the MEG spark plug in finger tight and then retighten 1/2 a turn for plugs with a gasket and a 1/16 of a turn for conical and taper seat plugs without a gasket. This is applicable for 10mm, 12mm and 14mm spark plugs only. Almost all cars and light commercial vehicles use 14mm spark plugs. If the plug is too loose, it will not be able to dissipate sufficient heat from the combustion chamber into the cylinder head and will overheat. If the plug is too tight, it may break during the installation or during engine operation.