Oil sludge happens when the engine’s oil breaks down and starts to combine with dirt, metallic particles, and other contaminates.

Examples of engines filled with sludge

The result is a thick, sticky hell stew that collects on valve covers, gaskets, hoses, and other critical engine components.

While brand new oil is a relatively clear, free-flowing liquid that lubricates and protects the engine, sludge slowly chokes the engine by increasing friction and heat.

Automakers are quick to blame sludge on maintenance habits. And yes, one of the top reasons sludge develops is because an owner forgets or puts off their oil change. However, that isn’t always the case.

Certain engines have a pre-disposition for this problem even if they’re meticulously maintained. This is usually due to defects in the crankcase ventilation or cooling systems.

Engines Pre-Disposed to This Hell Stew

Photo of Chrysler LH

Chrysler 2.7L LH Engine

Chrysler's 2.7L engine suffers from a number of design and mechanical defects that make the engine highly suceptible to oil sludge and contamination.

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Photo of Toyota MZ

Toyota 3.0L MZ Engine

Despite settling lawsuits, Toyota has staunchly maintained that the problems are the owners fault. They are lying.

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Vehicles with the Most Sludge Complaints

Full List of Vehicles

What Owners Are Saying