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Coolant In Oil: Symptoms, Causes & Fixes

Two of your vehicle’s most vital fluids are oil and coolant. They guarantee the life of your engine—if all parts are carefully monitored and maintained on a regular basis. One sign of trouble, for example, is the coolant in your oil. There are a few different ways that coolant can leak into the motor’s oil, but before that ever occurs, you should also become familiar with the signs of coolant in the oil. When you know what to look for, you can prevent an even more severe problem from happening to your engine, such as loss of power, lack of lubrication, or total engine failure.

Signs And Symptoms of Coolant in Oil

One of the first signs of coolant mixing with oil can be found when you are checking your oil level. When you look at the dipstick, and the fluid appears to be rather milky, you might have coolant in the oil. Here are other signs to watch for.


Coolant Loss

One imperative sign involves having a constantly decreasing level of your coolant but without any leaking from underneath the car onto the pavement or coolant dripping out of the exhaust pipe. Also, if you find that you must add more than a pint of coolant during each oil change, that is not normal. It’s a sign that your cooling system is in trouble. Because this system could be compromised, and you don’t see the coolant coming out of the car, then it’s mixing with the oil.

Syrupy, Sweet Smell

When you check the oil, you may notice that it has a musky, earthy smell. Conversely, coolant smells extremely sweet, almost to the point of unbearable. Therefore, you can easily tell the difference between the odors of each fluid. With that in mind, when you go to check your oil, and you smell even the slightest hint of something sweet on the dipstick, you have coolant leaking into your oil. This is another way to find for sure if the coolant is mixing with the oil even after noticing the drop in its levels without any external leaks. 

Milky Color

Aside from the difference in odor, you’ll see a change in your oil’s color and consistency if it mixes with the coolant. By itself, oil always looks dark and has a thick consistency. Once the coolant starts leaking into the crankcase, however, you’ll see a small stream of orange, green, or red floating in your oil. Unfortunately, if you run the engine, the crankshaft and oil pump will mix the two fluids together into what’s called “the dreaded milkshake.” The mixture gets its name from its resemblance to a chocolate milkshake on the surface. At this point, this gooey mixture has already circulated around the engine’s pathways leading to a bearing that demolished beyond repair due to lack of lubrication.


Puff Of White Smoke

Also, if you see white smoke puffing out of the exhaust pipe, and it has a strong, sweet odor, this also tells you that you have coolant mixing with the oil. You might even see an increase in your oil’s level when this occurs, but this points toward a large amount of coolant entering the crankshaft along with the oil. In this situation, you should immediately turn off the ignition.

What Causes Coolant to Mix with Oil?

Although engines are designed in such a way that coolant would never mix with oil, there are mishaps that cause this to happen.

Leaking Head Gasket

The cylinder head, which is located at the top of the engine’s block, has a head gasket which seals off the area between the head and the block. If this seal fails even slightly, coolant can leak into the oil.



Overheating causes damage to the head gasket which breaks the barrier between the oil and the coolant. Thus, they circulate through the wrong pathways and mix.

Damaged Oil Cooler

In the case of some vehicles, the oil cooler is surrounded by a larger chamber that holds the coolant. As the oil cooler circulates the oil, the separate coolant chamber keeps the oil’s temperature down. However, if the oil cooler is damaged, then you can have coolant leaking into the oil.

Damaged Engine Block

Blocks can last for many years and are almost foolproof. However, if you don’t change the oil often enough, the block can crack. This also leads to the coolant leaking or poor coolant circulation.

How To Fix Coolant in Oil

First off, if you suspect that the coolant is leaking in the oil, turn off your car immediately, or refrain from turning on the ignition. This keeps the mix of fluids from circulating and causing serious damage to your engine.

One possible fix is to apply a sealant on the radiator, but that may not address the issue of a damaged head gasket or a broken oil cooler. The ideal route toward fixing this problem is to allow a mechanic to look under the hood and diagnose the cause. Anything related to a damaged oil cooler or a gasket that needs replacing should be done by a licensed professional. Plus, another thing to keep in mind is that a mechanic would have the proper equipment to check for further damage like a cracked engine block. If that is the case, then you will need a whole new engine—or a new vehicle.

To prolong the life of your car, you need the best fluids that enhance its functionality while performing the two most important tasks—cooling the engine and lubricating it. Shield Lubricants are the leading producers and worldwide exporters of top-performing oil, lubes, and coolants. Your vehicle is one of your most important investments. Therefore, using products that have been certified and proven to lengthen its life and keep it running smoothly will save on costly repairs and keep your engine safe from major malfunctions.

Shield Polar Cool

Are you not sure if your engine’s fluids are up to par? We also offer testing on your lubricants with results sent to you 3 days after receiving your sample. Find out more about our products for industrial, automotive, and marine industries by contacting Shield Lubricants.

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