While overhauling an engine one has to fit new main & ConRod bearings & retain the old set for analysis on one side as they are likely to give a picture of the situation on roads. Some of the causes can include; B) Lack of lubrication, C) Contamination by dirt, D) Overloading, E) Corrosion, these are among the causes of bearing failure and appropriate measures have to be taken before re-assembling the engine to eliminate the re-occurrence. Whenever inspecting the bearings, they ought to be pulled out from the specific position and placed on a clean surface for the purpose of relating any deficiencies to the crankshaft journal. It is necessary to mention that contaminants can get into the oil during assembly, through the filters, or through the PCV system and can include metal chips and abrasives resulting from machining or insufficient cleaning. These foreign particles can be incorporated in to the bearing material, while large particles are likely to cause scoring or gouging. This is why maintenance such as cleaning of all parts, also changing oil and filter should be strictly observed. It can be caused by heat, over loading, leakage of oil and blocked passages and as a result, the bearing materials will be rubbed off and will over heat. Regarding the driving habits, there are some day-to-day habits affecting the bearing's lifecycle; for example, running the engine at a low speed in high gears which creates pressure or half/trip travel which may result in corrosion-heat. Besides, distortion of bearings could be caused by improper installation and this leads to conditions such as limited oil supply or the presence of high-spots, which leads to failure.