During an overhaul of the engine, the main and connecting rod bearings should be replaced with new ones. However, the bearings should not be discarded as they will also provide insight into the engine. Bearing failure can occur for many reasons, including lack of lubrication, dirt contamination, overloading and corrosion. These must first be dealt with before reassembling the engine. Bearings must be taken out from the engine components. They must be laid sequentially in their original position so as to help relate any problem with the bearing scallop on the crankshaft journal. During assembly of the engine, the filters or even the oil can introduce contaminants. Any metal chips or abrasives will be embedded within the bearing material and can score or gouge. To avoid failure, the engine thoroughly cleans all parts and regularly oiling and filtering changes are a must. When a bearing experiences excessive heat, overloading, oil leakage or blocked passages, it may suffer from a lack of lubrication. This causes serious damage. The bearing material gets wiped off from its backing. The driving habits also affect bearing life. Example: full throttle low-speed running creates large loads that squeeze out the oil film. Also, short trips do not allow adequate heating of the bearings to evaporate water and gas. This allows acid formation in the oil due to corrosion. Moreover, if the bearing is not installed correctly and there is a tight fit (or dirt behind inserts), the bearing will fail due to oil starvation.