At anytime an engine is overhauled it becomes necessary to replace main and connecting rod bearings while retaining the old ones as they can tell a lot about the engine. General causes of bearing failure include inadequate lubrication, polluted lubricants, overloading, and corrosion and all these must be corrected before the bearings can be reused. When examining the bearings, they need to be unloaded from their place and placed on a clean surface so that it may be easy to match the defects with the crankshaft journal. These particles can get into the engine when the engine is being assembled, with the filter or during the course of machining for they can penetrate deep into the bearing material and remain therein, while the larger ones cause scoring. It is from such failures that one can chose to emphasize the need for cleaning every part of the vehicle and following recommended times for oil change and filter replacement. The main causes include excess temperature, overcharge, oil loss, or blocked oil supply passages, with severe effect in that the bearing material is scraped off. Some driving behavior also affect bearing years; for example, maneuvering at slow speeds puts full throttle which can generate loads that expel oil and short trips result to corrosion. Also, improper installation like backlash of tight-fitting bearing or foreign objects trapped within can lead to oil starvation, and therefore failure.