Remanufactured engine is totally remanufactured by the companies to the original blueprints and exact specifications, and is tested to original equipment standards. There is nothing short in it from the new engine, but just the name it carries—remanufactured! However, in case of rebuilt engine, the repair is done upto the level of failure. This directly means that the engine has been repaired upto the level of failure for which there was a need of rebuilding; but apart from that, components are left intact. The testing procedure of rebuilt engine depends upon the individual rebuilder from whom you are getting the job done.
It is pretty clear from the basic difference between the two that the quality aspect of a remanufactured engine is far superior. It is made sure that all the parts of the engine are upto to the specification marks and nothing is left for let-it-go. But in case of a rebuilt engine, only failed and worn out parts are replaced. What happens in this case is that the frequency of the need of service is uncertain and sometimes more. Moreover, you are left with the craftsmanship of the rebuilder to get you a reliable rebuilt engine that can match your demands. It directly indicates that you are at more risk of getting frustrated due to the repeated failures of engine parts, which were left untouched at the time of reuilding.
You need to know what you pay for what! It is clear and obvious that the cost of rebuilt engine is far less as compared to the remanufactured engine; but as the price so is the quality. Rebuilt engine has more downtime and frequent service needs, while time is saved in case of remanufactured engine. The reason for this additional downtime and frequent need of service for rebuilt engine is because the components are replaced as per need, and no thorough testing is done to ensure that all the parts are reliable.
One more advantage for remanufactured engine is that you get a comprehensive and wholesome warranty periods from the company. The warranty period of rebuilt engine's parts is in fringes and is not that comprehensive. So it goes without saying that there is a big difference between reality and appearance—rebuilt engine may appear alluring, but in reality, remanufactured engines are more quality filled and of course valuable for your money.
It is clear that the situation depends upon your requirement and what money you can spend on your vehicle's engine. If you drive less, and consequently, have lesser needs of service, you could go for rebuilt engine, which is less expansive. However, if you have heavy work and can not afford a breakdown in your work, you should never compromise in quality and should straightaway go for remanufactured engine. It is costly but it worths it, and no wonder you will know that immediately!