Properly rebuilt tractor engines are as durable as new engines but typically lack some of the advances of newer models, such as emissions controls, maintains Engine Builder Magazine. The biggest advantage to rebuilding an engine is the cost when compared to buying a new one.
Older tractor engines are simpler than newer models and easier to repair. Some older tractors also work best in conjunction with the older engines. In that case, rebuilding an original engine extends the length of use of the tractor and makes it easy for the owner to do his own repairs on site. On the other hand, new engines offer options not available in older models that improve productivity in the long term.