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Is an Engine Flush Good or Bad?

Is engine flush good or bad? You will hear lots of arguments on both sides in various online forums. However, most car experts will suggest against it while mechanics and people running car servicing shops will speak in its favor.

An engine flush is a process of cleaning up the sludge and gunk deposited in your engine for years. You have to add a chemical additive to the oil and pour the mixture through the oil filler cap. Idle the car for 10-15 minutes, allowing the additive-mixed oil to circulate through all the engine parts and dissolving the dirt deposits. Then, you have to flush the oil, replace the oil filter, and fill up the engine tank with fresh oil.

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How Does the Sludge Form Inside the Engine?

Not changing the oil regularly is the main reason for forming deposits and sludge inside the engine components. Some drivers have the habit of going too long between oil changes and some even don’t bother about it unless the engine shows any warning sign.

engine flush good or bad
Flushing can clear up the sludge buildup.

Other two common causes of gunk buildup are:

  • Doing mostly stop-and-go driving
  • Leaving the car in the garage for months

Not driving the car for a long time will jam the engine components. It happens mostly in winter when condensation builds up because extreme cold does not let the oil to circulate in all the engine parts.

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Is Doing an Engine Flush Good or Bad?

Flushing is not necessary for an engine getting the oil changed at manufacturer’s prescribed intervals or as per the mileage and driving conditions. Besides, the owner’s manual never suggests the flushing of the engine.

However, a flush is not a bad idea if you are spending money on a used car that has driven 100,000 km or more and has a history of not changing oil regularly. In fact, not changing the oil can create a visible sludge buildup in cars that run far less than 100,000 km. Thick layers of deposits can cause severe drivability issues, engine light to come on, badly damaged crank, blocking of the oil pickup tube, and more problems. 

As flushing washes gunk and dirt out of the engine’s mechanism, it is not a bad option when needed. Also, it cleans up the engine components and keeps the new oil clear from dirt and other particles.

engine flushing
Engine flushing can save an old car.

So, if you are facing the dilemma of engine flush good or bad, you should take the decision after examining the vehicle’s condition. If it’s an old car and has many miles on it, you should choose this option. Flushing will clean up the engine and keep the car running for many more miles. However, a well-maintained and serviced car that changes the oil regularly won’t need it. The truth is most cars will never need an engine flush.

  1. saqib rana says

    very well described,


  2. Asenla says

    Is it harmful to apply on animals wounds?

  3. Kristine says

    I just had the gasket seal replaced on the engine block, along with the water pump replaced and radiator replaced. The shop also did an engine flush without asking me and said I needed to bring it back in 2-3 days later. My problem is that I can’t get back to the shop for 2 weeks since its 2 hours from my house. My car isn’t that old (2009 Toyota Camry), but they kept telling me it had some foreign substance in it from previous work. I regularly get oil changes and fix things when required. I didn’t pay for the engine flush so I know they weren’t trying to up sell me, but I’m concerned as to what its going to do to my engine. I think waiting 2 weeks to finish things might harm it. Do I take it to another shop and if so, what do I tell them besides what was done? I’m worried about my transmission blowing. I went to this service shop on a recommendation of someone else so I’m a little nervous about all this. Car broke down unexpectedly.

  4. William says

    Just Great Informative article. Lots of information about engine flush. Many many thanks for sharing with us.


  5. jai bhadouriya says

    Carwell India is offer best car service in kanpur

  6. William says

    I have a 2013 Nissan maxima which I purchased in 2015 with 543 miles, now it only has 23,000 miles but I never changed the oil. the service engine light came on and I took it to a Nissan dealership and they said that they will need to do extensive work to remove the sludge, can I flush the engine or is that not recommended?

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