When you need to replace your engine there will be some choices along the way. One of the most important choices will be when deciding to simply buy a used engine, or instead to go the re-manufactured route. So let’s start with some definitions.
A used engine is just that. An engine recovered from it’s previous use when sold new. It is typically sold as engine only without accessories, meaning you will need to buy a water pump, an oil pump, an air-conditioning compressor, etc. or use these accessories from the old engine you are replacing.
A re-manufactured engine starts as a used engine and then it is torn down, the worn or damaged parts replaced, and reassembled.
Since they both start with a used engine, and then one has to be torn down, and some of the parts will need to be replaced, and it will have to be reassembled, and the mechanic doing all of this must be paid, then you would expect the re-manufactured engine to be more expensive. In most cases it is, but not as much more expensive as you would expect, and in our opinion, well worth the money.

Consider this: You have one car to fix so you are going to buy one used engine. Therefore, you will pay the retail price for the used engine you buy. On the other hand a company that sells re-manufactured engines, re-manufactures lots and lots of engines, so when they buy a used engine to start with, they buy thousands of them all at the same time at a greatly discounted wholesale price. They can then put a lot of money into the work done on the engine before it even costs the same as the retail price of the used engine.
When you buy the used engine, some of the engine parts will be just as good as they were when they were new, and some of the parts will be worn out a bit. How many parts will be worn and how severely damaged they are will depend a lot on the condition of the used engine which you really can not well judge before buying it.
When you buy the re-manufactured engine some of the parts from the used engine will still be, in fact, just as good as new, and the rest will be replaced with new parts!
Let’s take a case in point. Like we said at the beginning, the used engine will be sold without accessories and that would include no oil pump. So in our scenario the company selling the used engine notices that the engine has low oil pressure. Well, it would be only natural for them to assume that when you buy the used engine and put a shiny new oil pump on it that the oil pressure will be just fine.
In a lot of cases they will be right, but a weak oil pump is only one of the causes of low oil pressure. What if the low reading they are getting is not caused by a weak or faulty oil pump? You buy the engine, you put on a new pump, the oil pressure is low, you have a costly investigate and repair to do.
What you should do is go into any auto parts store and look at engine gasket sets. An engine gasket set will be packaged for a specific engine and it contains the most common gaskets you will need to replace if you tear down and re-build the engine. See how many gaskets there are? Depending on which engine it is there could be a dozen gaskets in the set meaning there are a dozen gaskets in your engine. Some engines have as many as twenty or so gaskets in them. Now imagine a small crack in any one of those gaskets. Any crack or rip or tear in any of those gaskets would likely lead to a loss of oil pressure. So now is the time to realize that every one of those gaskets in your engine would be brand new if it were a re-manufactured engine.
Oil pressure is just one of the things that could go wrong with an engine, and just an example we have used here. With a re-manufactured engine the worn parts are replaced heading off potential problems down the road. You get a lot more peace of mind with a re-manufactured engine for the few extra dollars.
Another thing to consider is the availability of parts. Consider this: You buy a used engine. As it turns out there is a crack in the oil pan so you need a new one. It is a simple fix really. Then you start hunting and there do not seem to be ANY of that model’s oil pans available anywhere. You can delay your rebuild while you hunt salvage yards, but there is really little else you could do.
If you go the route of the re-manufactured engine you will not have this problem because whomever re-manufactured the engine has already scouted out and acquired all the parts.
There is one other reason why it might be a really good idea to rely on the re-manufactured engine rather than a used engine. Service bulletins!
That’s right, service bulletins or re-calls, or manufacturers updates, or what ever you want to call them. Every year cars are manufactured and sold. Of course, as they are building the car they follow spec, but sometimes the specs change. Sometimes, in fact, the specs change after the car is sold and that is when the manufacturer does a recall.
Most times the recall is for some part of the car that is not the engine, but sometimes the engine is involved. So consider the used engine. In most cases you have no history on the engine itself. If the engine and car were built in 2012, and the car was crashed in 2013, and if an important service bulletin was released in 2014, and if you buy the used engine in 2015, then there is a real good chance that the service bulletin was NOT applied to the engine you just paid good money for.
On the other hand, any reputable re-manufacturer is going to have updated specs when he re-builds the engine. In other words the specs that they use will INCLUDE all service bulletins at the time they re-manufacture it specifically including the service bulletins after the car was originally sold.
Some of these service bulletins may have little effect on your engine, but some of them may be really important safety problems that need to be addressed before you put your family in the car.