Antifreeze in Oil: What You Should Do | Autance

Antifreeze getting onto engine oil can, at first at least, seem like a disaster. They are two liquids that perform…

  • 356
Antifreeze in Oil: What You Should Do | Autance © Antifreeze in Oil: What You Should Do | Autance

Antifreeze getting onto engine oil can, at first at least, seem like a disaster. They are two liquids that perform very different functions within the vehicle, and as such have very different chemical compositions.

What does that actually mean in reality? Well it means that they shouldn’t really mix. If they have however then don’t worry, it’s not the end of the world! In this article we are going to take a quick look at what you should do if you suspect that antifreeze has made it’s way into your vehicle engine oil.

The first thing we have to stress though is:

Related Post: Best Anti Freeze

Don’t Panic!

The first thing we have to stress is that this is not an engine killer, so first of all keep calm. In fact, as we go onto explain below, there is a chance that you have been driving around with anti-freeze in your oil for a while, and the car probably hasn’t exploded yet we’re going to guess.

The solutions to the issue are also pretty straightforward (again something we will get to later in the article). So if you suspect, or know for a fact, that antifreeze has entered your engine oil there really is not a huge cause for concern.

Ok, if your engine was oil free – we mean totally bone dry of any lubrication – and you poured in antifreeze and started the ignition, then you would probably be looking for a new engine right about now.

Instead you’ve basically watered down the oil with a little (or a lot) antifreeze. So that’s fine right?

Well, yes and no, because:

It Is a Problem!

No it’s not the end of the world, but it is still an issue that you need to take care off.

Engine oil you see is very thick. That is because it is designed to work by coating the moving surfaces of the engine. When it does this, it helps to protect against damage from friction and wear and tear. It also works to remove excess heat from the engine.

Antifreeze is very thin and runny. It is designed to be added to the coolant system in the engine to lower the freezing temperature and raise the boiling temperature. This protects the cooling system itself from damage (say from burst frozen pipes) and also plays a huge part in helping the engine remove excess heat.

When the two liquids meet, they do not play well. The anti-freeze will stop the engine oil bonding effectively with the engine parts. That in turn means the engine oil is able to provide less lubrication.

There are also a number of chemicals included as ingredients in antifreeze that are not designed for repeated close contact with the engine components. If they are in prolonged contact these chemicals can really do some damage inside the engine. For that reason antifreeze should be removed from the engine oil as soon as possible.

So what do you do about it? Well, that will really depend on when you noticed the issues, and more specifically if the engine has been started after antifreeze was noted in the oil.

What to Do If The Vehicle Engine Was NOT Started

If you know there is antifreeze in the engine oil and the engine has not been started then the solution is pretty simple. You will probably be in this position if you were careless and added antifreeze down the engine oil neck by accident.

First off, don’t worry – it’s really a pretty common mistake, or we wouldn’t bother writing this article!

 The second thing to know is that you should not start the engine under any circumstances. If you do start the engine, then unfortunately the rest of this section is null and void, and you need to drop down to the other way to remove anti-freeze from engine oil.

If you were lucky or smart (and sometime they are the same thing!) and did not start the engine, congratulations, you just saved yourself a world of time and money.

So the antifreeze is in the engine oil, but the engine has not been started. Here is the step-by-step guide of what to do:

  • Nothing! Yep, do nothing. Well, do nothing for about an hour or so. This is because, as we said above, antifreeze and engine oil do not mix well! So if you leave the car alone for just an hour or so, the antifreeze will sink to the bottom of the oil sump.
  • After you’ve left the car to sit for a while, you need to get yourself an oil drain pan or a shallow bucket. Remove the sump plug and start to drain the contents. As it settled to the bottom, you should see the antifreeze exit the system first. Continue to drain until all you are seeing is clean oil.
  • Top up the system with fresh oil – remember, not antifreeze again!
  • If you want to be extra safe, you could drain all the oil either now or after a few days and replace it all with a fresh lot.

What to Do if the Vehicle Engine WAS Started

If you have been driving around with antifreeze in the oil for a while, then you need to get onto that issue pronto. You will probably diagnose the problem here by seeing brown bubbles or crusty, dried up brown residue on your dipstick. Or if you drain your oil (or see inside the sump) and it looks like chocolate milk, they are both good indicators of a leak of antifreeze into the engine oil.

Blown head gaskets or leaky seals could cause this. Whatever the cause, you need to clean that gunk out, so:

  • Drain the system. No point waiting this time as the antifreeze is all mixed in already. Drain it all and drain it straight away.
  • Do a full oil change including replacing the filter.
  • Drive the car as normal for a day or two.
  • Perform a second full drain, replace with fresh oil and replace the filter (again).
  • Find out how the antifreeze is getting into the oil and fix that problem too, or take it to a mechanic.


That’s about it folks! Yes it can be annoying to have to perform multiple oil changes. But it’s a whole lot easier and cheaper than having to replace your entire engine! Don’t panic, act quickly and flush all traces of antifreeze from the system and your car will be just fine.


  1. How to Check the 5 Essential Fluids in Your Car – YourMechanic
  2. How to Fix an Antifreeze Leak – HowStuffWorks
Commnets 0
Leave A Comment