What Is Oil Sludge and How Does It Hurt My Car?

Sticky, dirty oil sludge is the result of oxidation and/or contamination of engine oil. It becomes a thick gel that sticks to engine parts, which blocks or hampers oil flow through the engine. It is important to keep that full flow going to prevent placing additional stress on the radiator and the entire engine cooling system. If your oil flow weakens, you’ll notice a reduction in oil pressure and fuel efficiency. Regular oil changes can help you avoid damage to the engine and other expensive parts, such as timing belts and idle controls.

How Is It Formed?

Because engine oil is unstable, it oxidizes when exposed to oxygen and high temperatures. Oxidation can occur quickly when the oil continues to be held at extreme temperatures over an extended period of time. The molecules in engine oil break down during oxidation and combine with dirt, fuel, metallic particles, water, gases and coolant. This mixture becomes the sticky sludge. This sludge stores heat instead of releasing it, which makes harder work for the radiator and cooling system.

Reasons for the Buildup

Motor oil sludge first appears on top of the engine, as well as the valve cover and inside the oil pan. It can then block the siphon on the oil screen and prevent oil circulation in the engine. Buildup can occur when the car is driven repeatedly in heavy traffic. Long periods of stop-and-go driving can contribute, and even frequent driving for short distances can cause sludge.

How to Avoid Buildup

When you start the car, keep an eye on the dashboard. Does the “check engine” or “oil change” light come on? Both can signify that the oil needs to be changed. Additional preventive measures include:

  • Consult your owner’s manual for guidelines on how often to change the motor oil and stick to a schedule for changing it. Be sure to have the mechanic check for and clean out any oil sludge as needed.
  • Avoid heavy stop-and-go traffic if possible. Take different routes around traffic-clogged streets.
  • Check the dashboard gauge often to see if the engine is overheating.

Keep an Eye Out for Signs

You can help keep your car engine purring with regular oil changes and cleaning of sludge buildup. Your car does try to tell you when there’s something wrong, and you can hear what it’s saying by keeping an eye on the gauges and dashboard lights and by listening for any unusual sounds.