Sludge can be the result of poor maintenance. But it can also be the sign of a more serious engine defect.

As oil roams through the engine, additives in the oil absorb soot, dirt, water, metallic particles, excess fuel, and anything else that keep the engine from running efficiently. Oil starts to thicken once it reaches its absortion capacity.

More friction = more heat. More heat = more sludge. More sludge = more friction. Rinse and repeat.

Signs of Sludge

  • Loss of oil pressure
  • Higher engine temperatures
  • Rough acceleration
  • Poor gas mileage
  • Engine stalling
  • Scornful looks from mechanics

While it's important to know your oil's lifespan and how long it's been in the engine, it's also important to pay attention to your engine's specific consumption habits.

The more concerning causes of oil sludge have to do with defects in the engine.

Crankcase Ventilation System Defect

Oil sludge can be the result of a poorly designed or defective crankcase ventilation system, like the one found in the 1998–2005 DaimlerChrysler’s 2.7L engine. This engine is notorious for allowing hydrocarbons to enter the oil and break down the additives that help gather all the gunk.

A crankcase filled with sludge
A sludged-up crancase shows how extreme the problem can get

Additionally, water pump gasket failures have been known to leak coolant into the oil. And all those extra contaminates can severely degrade the oil’s life.

These issues have caused an incredible amount of sludgy complaints from owners of the Concorde, Sebring, Intrepid and Stratus.

Engine Operating Temperature

Oil oxidizes the most when the engine’s operating temperature is too high. The oxidation only gets worse when that heat lasts a long time.

Volkswagen’s 1.8L turbocharged engines have a history of sludge-related complaints. From 1997-2005 their turbocharged engines came equipped with a tiny 3.7-quart oil capacity. And mechanics say it doesn’t provide the engine enough oil to dissipate the heat and it removes all margin of error for owners who may be a little late on their oil change.

Tips to Prevent Sludge