Often drivers who have relatively old cars break down may be left with a choice between a used engine or a remanufactured engine and want to figure out which choice offers the better value in the short and long term. The answer is that it depends, but that remanufactured engines are usually going to be the better deal in the long run.
While used engines are cheaper up front, there are also greater risks in terms of the quality of the motor and that can lead to bad surprises. Remanufactured engines on the other hand are tested to certain specifications and may include warranties from the remanufacturer. As a result, they are more reliable in general than used engines.
Used engines are simply pulled out of a car that is no longer running and tested to make sure that they are working, then placed into a new vehicle. Depending on the reliability, depth and accuracy of the testing, used engines can be a big gamble.
Still, there are situations in which each option clearly makes more sense than the alternative.