Saving money is the main benefit of rebuilding an engine instead of buying a new one, but a drawback is the age of the parts. Depending on the make and model of car, a rebuild could be as low as half the cost of a new engine.
Cars are built to last for a long time and do not rust out except in extreme weather conditions. If the transmission and suspension are still in good shape, a rebuilt engine may be able to double the lifetime miles of the car. Rebuilding often improves an engine’s efficiency and reduces fuel costs because all of the cylinders are bored out, and internal parts such as gaskets, bearings, camshafts and piston rings are replaced in the process. This allows a driver to save an older car with nostalgic value at a reasonable cost.
The primary drawback to choosing a rebuild over a new engine is that the main components of the engine are older. Only the internal parts are replaced in most cases, so the engine block itself could have defects that are not corrected during the rebuild. A new engine typically has a longer lifespan than a rebuilt engine because there is no accumulated wear and tear on any of the parts.