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How To Remove Engine Sludge In 5 Easy Steps

Engine sludge is exactly what it sounds like: an accumulation of dark, greasy, and tarry deposits inside the engine crankcase.

It doesn’t sound pleasing, right? Engines are designed to run with clean motor oil. With the presence of engine sludge, the oil will be unable to lubricate and cool the engine.


What Causes Engine Sludge?

What Causes Engine Sludge?

Sludge is caused by the breakdown of oil. If you have a habit of using poor quality or cheap motor oils in your car or bike, then you need to know these facts:

1. The continued use of poor quality motor oils will cause the build-up of engine sludge.

2. Extended oil change intervals or not changing the oil and oil filter periodically will accelerate the formation of engine sludge.

Engine sludge is made up of oxidized motor oil, dirt, soot, water vapor, and leaked coolant. Using a good motor oil will keep all of these harmful contaminants suspended in the oil, ready to be flushed out on your next oil change.

If you have a nasty habit of not changing the oil on a regular basis, then you will most likely deal with engine sludge sometime in the future.

Symptoms Of Engine Sludge

If you notice these symptoms on your car or bike, then you should definitely check the motor for the presence of engine sludge.

  • Noisy hydraulic lifters or valve tappets
  • The oil warning light is ON while driving the car
  • Low oil pressure
  • The oil drains slowly when the drain plug is removed
  • The presence of dark greasy sludge on the rocker cover and oil filter

You can also check for the presence of engine sludge by pointing a flashlight inside the engine. Simply remove the oil cap and use a flashlight to check for accumulated sludge inside the valve cover.

If you do this, you will notice that the components are all covered in oil, but you should still see the metallic parts glistening in the light. If you see thick tarry deposits inside the valve cover, you might be dealing with a serious case of engine sludge.

Of course, the best way to determine the extent of the damage is to take the motor apart. In severe cases of sludge, you might need to buy a new motor.

How To Remove Engine Sludge In 5 Easy Steps

If you haven’t changed the oil in your car for more than 7,000 kilometers (or approximately 1 year) then you can expect a slight formation of engine sludge. Fear not. Here are the 5 easy steps on how to remove engine sludge.

Things You Need

  • Engine flush or oil flush treatment
  • Fresh motor oil
  • ​Container to catch the dirty oil
  • ​New oil filter
  • ​Oil filter wrench
  • Pressurized air (optional)

Step 1: Treat The Motor With Engine Flush

Treat The Motor With Engine Flush

Park your car is a safe and level area. Open the hood and remove the engine oil cap. Pour a can of engine flush or oil flush treatment inside the engine.

Tighten the engine oil cap and close the hood. Start the car, and let it idle for 10 to 15 minutes. DO NOT DRIVE THE CAR. Just let it idle and warm up thoroughly.

The engine flush will help to liquefy the sludge, making it easier to mix with the dirty oil so you can flush it out completely.

You can use a product like Sea Foam Motor Treatment or Liqui Moly Pro-Line Engine Flush, but you can use any type of engine flush from a reputable manufacturer.

Step 2: Turn Off The Engine And Drain The Oil

Drain The Oil

After the engine is all warmed up, it is time to turn off the engine and drain the oil. Simply remove the drain plug in the oil pan and let the dirty oil and sludge drain away. Use a clean container to catch the dirty oil.

Take your time while doing this. You can also use pressurized air to thoroughly clean and flush all the dirt inside the engine. Remove the oil cap, turn on the air compressor, and insert a hose inside the oil filler. The pressurized air will help to further loosen up the dirt and sludge inside the engine so it easily drains out of the motor.

Step 3: Install A New Oil Filter

Install A New Oil Filter

Loosen the oil filter using an oil filter wrench and allow the remaining oil to drain. Discard the dirty filter.

Grab the new oil filter and put a small amount of clean oil on the oil filter gasket.

Use only your hand to install the oil filter. Turn the oil filter in a clockwise direction to tighten.

After draining the dirty oil and installing a new oil filter, you should go ahead and reinstall the drain plug. You don’t want the fresh motor oil to flood your garage, right?

Step 4: Pour Fresh Motor Oil

Pour Fresh Motor Oil

Make sure that you are using the proper grade, weight, and rating of motor oil for your vehicle. When in doubt, refer to the service manual. Not using the right kind of motor oil will contribute to the formation of engine sludge.

Simply pour the motor oil and check the oil level via the dipstick. Do not overfill the motor with oil. The oil level should be in the middle of ADD and FULL.

Step 5: Screw The Oil Filler Cap Tightly

Screw The Oil Filler Cap Tightly

After pouring fresh motor oil and checking the oil level, screw the oil filler cap tightly, close the hood, and you’re done!

How To Prevent Engine Sludge

Here are a couple of tips that will help prevent the build-up of engine sludge inside the motor.

1. Regular oil changes. Make sure that your vehicle is serviced accordingly. Check the owner’s manual for the recommended service intervals.

2. Always use good quality motor oil and oil filter when changing the oil.

3. Avoid stop-and-go driving as much as possible. If your vehicle is subjected to extreme use, then you will need to change the oil more frequently.

4. If you have a diesel engine, it is wise to constantly maintain the integrity of your fuel system. If you detect any abnormalities such as hard starting, knocking, excess smoke, or poor performance, have your car or truck inspected by a qualified mechanic.


It is easy to remove the build-up of sludge inside your engine. Remember to always use a good quality motor oil whenever your vehicle is due for an oil change. It is also advisable to follow the service recommendations of your vehicle to prevent engine sludge from accumulating inside the motor.

About Jason Trevino

Jason is a talented and advanced author, blogger and auto expert. He is determined in researching thousands of products so as to make it easy for the owners to find the best products. He focuses on giving users better understanding on products they are using and ones they anticipate to buy.