An internal combustion engine is subject to wear. Regular maintenance, such as timely oil changes, and a responsible driving style – gently warming up and periodically loading the engine to reach a high temperature while preventing internal pollution – contribute to a longer lifespan. As components become dirty or worn, abnormal noises may occur, engine power may decrease, or oil consumption may increase. There can also be cause and effect relationships. For example, unburned oil entering the exhaust can cause damage to the catalytic converter.
When wear and tear is suspected, a diagnosis can be made based on measurements. This can be done using external measuring equipment on the engine, such as a compression test, or by examining and measuring disassembled parts with tools like a micrometer and cylinder wear meter.