How to Remove Motor Oil Sludge

Updated April 17, 2017

The build-up of sludge in your car's engine is caused by the breakdown of the engine oil. The oil breaks down due to factors such as heat and contamination. Over time, the oil will thicken, causing it to settle on the engine's components, such as the crankshaft or on top of the engine on the valve train. This will effect the engine's efficiency, causing it to run hotter with less lubrication. Complete engine failure can occur eventually. However, with proper care and maintenance, you can take steps to prevent this situation.

Flush the engine oil system. You can purchase a quality engine flush at your local auto parts store. Replace the vehicle's old oil filter with a new filter and add one bottle of engine oil system flush. Make sure the oil level is at its maximum safe limit, as indicated on the dipstick. Loosen the oil drain plug and allow some oil to drain into a catch basin before adding the engine oil flush. Tighten the drain plug again.

Turn on the engine. Allow it to idle for approximately 15 minutes. Do not rev the engine or put it into gear. Shut the engine down after 15 minutes.

Remove the engine flush. Remove the drain plug from the oil pan and allow the oil and flush to drain into a catch basin. Remove the oil filter and replace it with a new filter. Replace the oil drain plug after all the oil and flush have drained completely into the catch basin. The drainage should take at least 10 minutes.

Fill the engine with fresh engine oil that meets the vehicle manufacturer's recommended specifications. After adding oil, start and run the vehicle, turning it off after five minutes. Wait another five minutes and check the oil level again with the dipstick. You may need to add more oil.

Do a complete oil change with another new oil filter after approximately 100 miles of usage. This step is optional but serves to remove any remaining sludge that may have become dislodged after using the vehicle.


Remove the oil pan and inspect and clean the oil pickup screen after performing an engine flush on a vehicle with heavy sludge.


Be careful when flushing an engine with a heavy build-up of sludge. The flush could possibly dislodge the sludge into clumps that can become trapped in the oil pump pickup screen. A blocked screen will cause a severe decrease in oil pressure, which could lead to engine failure.

Things You'll Need

  • Engine flush
  • Engine oil
  • Oil filters
  • Catch basin
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About the Author

Melissa Morang began writing professionally in 2002. She has created sales scripts for telemarketing companies and contributes to online publications. Morang has a Bachelor of Arts in English from the University of Minnesota.