In most modern vehicles the compressor is mounted directly on the combustion engine; sharing its geartrain, oil and coolant supply. Therefore, any deviation in compressor design tolerance could also have a significant impact on the combustion engine. For example: a damaged compressor gear might block the engine geartrain, or metal particles might enter the oil or coolant circuit – causing significant damage and leading to expensive vehicle repairs and downtime. 

Instead of being manufactured from the highest quality materials, utilising strict process control by the company who designed them in the first place, non OE aftermarket parts are often reverse engineered and cheaply mass produced. These parts can significantly deviate from the original specification, meaning they won’t be such an exact vehicle fit, have the same part longevity or be manufactured from the same robust materials.