What is the probable cause of engine oil in the coolant? There are no performance issues but when I checked the coolant level, I noticed oil residue.

  • 1
    How much is "residue" ... some tiny spec of an amount? Or is it all over everything? Jul 19, 2016 at 21:17
  • 2
    Check your oil too, if oil is in the coolant it's bad, but if coolant has gotten in your oil and it is contaminated (frothy, milky, bubbly, emulsified) it's real bad and you should not drive the car. Jul 20, 2016 at 3:29

2 Answers 2

  • Nr. 1 cause: damaged head gasket
  • Nr. 2 cause: damaged oil cooler (if present)
  • Nr. 3 cause: cracks in the engine block/head

Check for coolant in your oil too (it'll look milky or frothy). If you have that, have your car towed to your garage of choice and get your head gasket replaced. It's not safe to drive!

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