I have purchased a pre-owned car. After the purchase I saw there was engine oil in the coolant reservoir and also the coolant level is going down slightly. Engine is not heating up.

What do I do?

What might be the reason?

  • What is the make, model and year of your car? Mar 18, 2016 at 19:49
  • How much oil are you taking about? If it is a very small amount and your oil level is not dropping, then the engine may have had a fault previously that has been repaired.
    – HandyHowie
    Mar 18, 2016 at 20:57

1 Answer 1


The first thing to check for when you have oil and coolant mixing is a blown head gasket. Check compression on all of your cylinders with a compression tester (you can borrow them from AutoZone or similar) and specifically look for one or two cylinders that have significantly lower compression than the others (in the range of 30+ psi difference). Another indicator is if you also have coolant mixing with your oil (run the engine, then pull the dipstick out, if it looks like it's covered in chocolate milk, that means there's water and therefore coolant in your oil). Along with that, I suspect that by "Engine is not heating up" you mean "the temperature gauge doesn't go up", which means your thermostat is probably defunct, which could have caused the kind of overheating that can damage head gaskets, so look into getting that repaired as well.

  • 1
    Autozone is a US parts retailer. He may not know what that is. We have users from across the globe. Mar 20, 2016 at 21:34
  • True, but I don't know the names of any foreign retailers, so I just said "or similar"
    – Ceshion
    Mar 20, 2016 at 22:05

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