These films play an important role in reducing friction and wear of the sliding surfaces. In an automotive engine, under normal operation, the lubricant film is generally present between the cylinder bore and piston ring. The thickness of the lubricant film varies in different lubrication regimes depending on the piston’s location within the cylinder bore. The most severe lubrication condition occurs when the piston is at the top dead center or in the bottom dead center of its cycle where the highest temperature and contact pressures occur; this regime is known as the boundary lubrication regime...
