Considering today’s competitive enviroment and the required emission regulations, it becomes increasingly important to reduce fuel consumption and harmful exhaust emissions in order to increase engine output power. This can be obtained by developing a well designed injection system or combustion chamber as well as by decreasing the mechanical losses, which are among the most important parameters affecting engine efficiency. The amount of wear rate and its location in the engine should be known to reduce mechanical losses. Therefore, piston ring-cylinder liner wear, which constitutes the greatest portion of mechanical losses, must be investigated. Researchers have attempted to measure the amount of wear by using various methods. In addition, there are also studies carried out to improve new coating materials or lubricants for reducing wear rate. In this study, these measurement methods are discussed and compared with each other in terms of their advantages and disadvantages.