Flushing a car's automatic transmission is a common service procedure. Many car dealers and independent oil-change shops offer it. Transmission flushing is a smart thing to do when a car has high mileage because it cleans out all the debris and gunk that has settled inside the transmission.

So, if transmission flushing makes so much sense, why aren't engine blocks flushed? After all, sludge can certainly build up inside a high-mileage engine. Well, to make a long story short, quite a few dealerships and repair shops are offering engine flushing procedures now.

How it's done

Engine oil flushing a simple procedure. It doesn't require the fancy flushing machine that transmissions do. Here's how it goes:

First, an automotive technician starts up the car's engine and then drains out the old oil after it's good and warm (engine off). Second, the engine is filled up with a special cleaning solution, the engine is started up and then is idled for a few minutes. When finished, the technician drains out the cleaning solution out and pours in fresh oil. Usually a new oil filter is installed at the same time.

When should engines be flushed?

Many older engines can benefit from having an oil flush, particularly cars with unknown maintenance records.  You just never know if the previous owner waited a long time in between oil changes and layers of sludge have built up. Sometimes you can even see the effects of this by looking in the oil filler cap. You might want to flush your engine after any major engine work too. This will remove any small metal particles and grit that is left over from the machining of parts.

When not to flush

Note that oil flushing is not always recommended! As matter of fact, some manufacturers advise against it. We spoke with the service department at Steve Jones Chrysler in Owensboro, KY and asked what the Chrysler policy is. As it turns out, Chrysler is one of those companies that does not always recommend oil flushing but says to call your local dealer for advice. Their belief is that by performing regular oil changes with the proper oil, engine flushes aren't necessary.

We also checked with a local Chevrolet dealer and discovered that GM suggests the same. In fact, they state in their manuals that "Engine oil flushes are not necessary. If oil is changed on schedule, you shouldn't have to flush the engine during the life of your car."


Check with your local brand dealer if you are thinking of having your engine flushed. Chances are it will help to clean out accumulated gung but if the manufacturer doesn't recommend it, its best to heed their advice.

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