Coolant In Oil: 6 Causes, 3 Symptoms & Cost to Fix

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coolant in oil

How often do you pop up your hood and pull the engine’s dipstick to check the oil? Perhaps you’re on this page and reading this article because you noticed something unusual on your engine oil. Does it look like your morning creamy coffee?

If yes, that’s your car’s coolant mixing with your engine oil, and that’s a serious trouble that needs an immediate solution to avoid that problem from causing another bigger problem. Coolant in oil indicates that there’s an internal engine leak. It might be an indication of a blown head gasket, or damaged cylinder head, or the head gasket.

When coolant mixes with oil, it deprives the oil’s lubricating qualities and can induce engine failure. Coolant can cause to slow the process of the oil by badly affecting its viscosity, rendering it more complicated to circulate throughout the oil chambers and lubricate your engine. Coolant in oil also impacts the engine by producing an acidic condition on the engine oil, leaving your vital engine components or, worse, your entire engine in danger.

In this article, we’ll be discussing the things you’ve probably thought about coolant in oil, how it got there, what’s causing this problem, and what you should do? Continue reading to understand and learn about things you should know regarding this kind of issue.

How To Determine If There’s Coolant In Oil

Dipstick assessment is a simple and inexpensive method for determining the presence of coolant in oil. When you notice brownish bubbles or a crusted brown residue over the oil level mark on your dipstick, coolant has gotten into your engine.

Another indicator of a coolant leak is white smoke coming from the exhaust pipe having a sweet aroma. The oil level could even increase in this circumstance, indicating that a significant quantity of coolant has leaked into your crankcase.

To examine, shut off your engine, let it rest for an hour or two before unthreading the oil drain plug, and catch the coolant using a clear container. Since coolant is denser than oil, it will gather at the bottom of your oil pan. After getting a few ounces, close the drain.

Inspect the fluid you gathered for water and glycol. The combination of water and glycol can create a dense mayonnaise-like mixture, relying on how long your coolant has been inside the crankcase. Additionally, a sweet coolant odor may be perceived.

Coolant has an incredibly nauseating sweetness, while oil has a gritty, musky aroma. When coolant loss is apparent, but so far, no leaks are seen, pull out the engine oil dipstick, then smell it. If even the faintest smell of sugar penetrates your smelling sense, your entire cooling system is probably blending coolant and engine oil.

When coolant mixes in your oil or oil in the radiator or coolant reservoir, it typically indicates that one or more seals or gaskets of your engine are broken. Your car’s engine is configured in such a way that one structure regulates engine oil to maintain lubrication and another manages coolant to prevent engine overheating.

Your cylinder head gasket is the a part of your engine that prevents oil and coolant from mixing. Therefore, if your engine has a blown head gasket, you might anticipate the oil and coolant will mix. Additionally, coolant and oil might mix if the engine overheats, resulting in a failing head gasket, or worse, a cracked cylinder head. Likewise, coolant and oil might mix due to an occurrence that left you with a cracked engine block or a broken cylinder head.

Causes Of Coolant In Oil

The very obvious and undeniable sign of coolant in your motor oil is when it develops a creamy coffee color. When your coolant contains oil, it must be changed. However, before replacing it, thoroughly cleanse first the entire system to ensure that the full coolant and motor oil mixture is gone. Following that, you must ascertain and fix the source of this headache-causing issue.

Blown Head Gasket

Coolant leaks into the oil if you have a blown cylinder head gasket. This results in the creamy coffee coloration of the motor oil in the engine. Also, this mixture will be visible in the coolant reservoir and radiator, which can be seen from the top. Additionally, a cloud of white sweet-scented smoke is noticeable when coolant escapes into the engine’s combustion chamber. You must check the radiator and water pump as these two components are prone to damage when oil and coolant mixture passes through them.

Oil Cooler Leaks

The oil cooler is supposed to split the coolant and oil in a separate room while accommodating them simultaneously. If your oil cooler has even minor internal flaws, that can be a reason for the trouble you are facing. When the oil cooler leaks, it can enter the coolant, but there will be no coolant in your oil.


An overheating engine is caused by several reasons, for instance, a faulty radiator and water pump, or a failing cooling system. And this root issue can cause multiple other damages. One of these damages can be your head gasket, which can cause your coolant and oil to pass and go out from their designated routes—causing the coolant to mix with the motor oil.

Damaged Engine Block

A broken engine block could result in mixing engine oil and coolant. This is the least likely occurrence since engine blocks are pretty durable. When the block gets damaged, your best course of action is to obtain another block or a whole new engine.

Leaking Transmission Cooler (Additional Possibility)

Another uncommon but likely to be a reason is a leaking transmission cooler. Numerous automobiles have a transmission cooler. Typically, this is a component of the radiator. When your transmission cooler develops some cracks, it’ll allow the coolant to blend with your transmission fluid. When this occurs, you can see the coolant becoming creamy. When coolant is leaking into your transmission, the result is disastrous. This might cause extensive damage to the transmission, requiring its replacement.

Signs And Symptoms Of Coolant In Oil

Engine oil mixing with coolant signifies a blown head gasket or an engine breakdown. It affects your oil’s lubricating and viscosity properties, leading to a decrease of lubrication and engine power, and can lead to engine damage. Below are a few signs to determine the presence of coolant in your oil.

Creamy Coffee Color

If coolant enters your oil pan, it leaves a green, red, orange, or brown mixture in the crankcase, relying on the kind of coolant you’re using. While the car runs, the coolant and oil mix, resulting in a creamy mixture. It’ll clog the engine channels. Therefore, if you pick out your dipstick and discover a creamy coffee color, this indicates the presence of a coolant-oil combination.

Coolant Loss

When you detect constant coolant level drop but no spills underneath the car, the coolant is most likely to leak on head gasket, or due to a cracked cylinder head, or coolant finding its entry to the oil pan. Therefore, do a leak inspection if you see a regular coolant loss. When no coolant leakage are found, you can inspect the oil level to determine if coolant is entering the crankcase.

Sweet Odor

If you detect a coolant loss that does not result in drips on the engine bay or underneath the car, the coolant has most likely lost its way to penetrate the oil pan. Coolant dissolved in the oil gives a pleasing sweet aroma. Another technique to determine whether coolant and oil have been mixed is removing the dipstick and smell it. Even a little coolant in the oil creates a particular sweet odor.

How To Fix

According to the nature of the problem, you may either DIY it or get an expert’s assistance. The culprit might be an overheated engine, a leaking head gasket, or a clogged oil cooler. The most frequent cause is a leaking head gasket.

Therefore, if you’re wondering how to cure coolant combined with motor oil. Mainly when the source of the problem is a leaking cylinder gasket. You may hire a professional to fix it along with any other internal damage, or you can do it yourself if you are equipped with complete knowledge and strength to face the issue and, yes, the physical equipment too. You know, the tools!

However, suppose you’re a newbie and want to try fixing stuff or don’t have a complete idea and just want to follow online instructions. In that case, we strictly recommend that you leave the problem and the solution to an experienced and qualified mechanic. Cylinder heads are sensitive components that require an expert hand to get the job done. You might not want to see your engine get additional problems from your own hands.


Numerous variables can influence the overall cost of this issue. For instance, if you need to repair the transmission cooler, you will need to change the radiator and conduct a transmission servicing. This task alone can cost from $350.00 up to $450.00. When you suffer a blown head gasket and require replacement, the cost could range between $1,200.00 up to $2,000.00.

However, if discovered, that the above-mentioned doesn’t cause the problem, the worst thing you might have is a cracked or damaged engine block. This nightmare of a damage may require an engine block replacement; however, choosing an entire engine replacement is best recommended. This is a very pricey repair, running between $4,000 up to $8,000.00.

Each of these instances is rather different. The said prices may vary depending on your car’s make and model, your location, and your engine size. But before getting to any assumptions, it is critical to identify the source of your issue. Once you’ve determined what’s leading the coolant to mix with engine oil, you can begin planning accordingly and deciding your next steps.


The mixing coolant and oil can severely harm your engine.  If you’re a car owner who maintains your automobile regularly, you may be able to prevent this issue. Poor vehicle maintenance and usage may cause engine damage. Your engine will not run correctly if these fluids mix up and cause damage.

The coolant in your oil is a significant concern, but getting it on early can save you time and money. We strongly suggest you have a competent technician to examine your engine if you sense a problem. This may prevent you from severe troubles and allow you to drive with more confidence.


What happens if coolant gets in oil?

When coolant is mixed with oil, it depletes the oil’s lubricating qualities and can cause your engine to fail. Thus, coolant in the oil produces a light brownish fluid that resembles creamy coffee.

How do I know if there is coolant in my oil?

When you find oil combined with coolant inside the reservoir tank, you will see thick, creamy stuff, which indicates that you’re experiencing this problem. You will also want to cleanse the reservoir tank thoroughly and rinse your radiator using water.

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