What Happens When Water Mixes With Oil in the Engine?

by Synthetic Oil | Last Updated: February 25, 2023

The primary purpose of engine oil is to lubricate the moving pieces and absorb the heat. To keep your engine in good condition, you give your car timely oil changes and other maintenance. However, with wear and tear, there is always a chance that the engine oil gets contaminated, including water. You may think that water would be harmless when mixed with oil, but the truth is that this could be problematic for your car. Here is what happens when water mixes with oil in the engine: reduced effectiveness, rust, and corrosion.

Now, let’s learn what causes water to contaminate the engine oil.

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What Does Water in Engine Oil Do To Your Car?

Engine oil contains several additional ingredients, including detergents, dispersants, inhibitors, antioxidants, and other components that help the oil perform better. When there is water in engine oil, the additives cannot work to their maximum effect. Water not only dilutes additives, but it also counteracts the oil’s lubricating efforts, increasing heat and friction.

Should there be a lot of water, your engine may end up destroyed.

How To Tell if There is Water in Engine Oil

If you want to know if there is water in your engine oil, the first thing you have to do is check out the dipstick. Let the engine cool for about 5-15 minutes after use before popping the hood. Pull the dipstick from the reservoir. Do you see any air bubbles? What about a residue that is above the oil level? Does the oil look like melted chocolate ice cream or a milkshake? Your engine may have water in the oil.

Should you suspect that there is indeed water in the oil, the next step is to check the drain pan. If you recall from science class, water, and oil do not mix. If you try to shake water and oil to blend them, the water and oil eventually separate, leading to oil on the top and water on the bottom. Well, the same thing happens in the oil reservoir.

Get under your vehicle and open the oil plug just enough for some oil to escape into a collection bucket. If the oil is milky, there is possibly coolant or water in the engine oil.

Sweet Smelling Exhaust

Another way to tell if there is water in the engine oil is by the exhaust. Turn your car on and put your sniffer near the exhaust pipe. Do the fumes smell a little sweet? If it does, it is a surefire sign that there is coolant or water in the engine oil that is burning off in the engine.

What May Be The Cause of Water Mixed With Engine Oil?

There are a couple of common (and not-so-common) reasons there is water in the motor oil. Let’s take a look at each one:

Condensation or Cold Engine Blowby

Guess what? The water may be getting in there through the natural process of condensation. At certain temperatures, water vapors will condense into a liquid. This can happen in the engine when combustion gases or cool air pass through the engine, settling on cooler surfaces and condensing.

However, that water will usually burn off without affecting your engine’s oil or performance. There is a more serious reason this could happen: running your engine cold or a clogged PCV system.

When you see steam coming from the tailpipe on cold mornings, it is because internal combustion is producing water at the same time it is burning fuel. That is why your vehicle will have a small hole at the bottom of the muffler to keep water from gathering inside. Yet, should some water become steam while the engine is still cold, it will bypass the piston rings, becoming blowby. Usually, the PCV system takes care of this blowby, but not a clogged one.

If you happen to be running your engine cold, only going on short trips, or have a clogged PCV system, then the chance of condensation or cold engine blowby increases.

Damaged Cylinder Gasket

Head gaskets undergo a lot of pressure, vibrations, and heat throughout the years. When a cylinder gasket decides to blow, it may cause oil leaks, coolant leaks, compression leaks into the crankcase, and more. You will know that the head gasket between the coolant and oil has broken when your engine oil looks like a milkshake instead of actual motor oil.

Damaged Seals

A damaged seal can cause a coolant leak, allowing water to get into the oil sump. Again, the oil will look milky and frothy when you go to check the dipstick.

Cracked Engine Block

When an engine overheats, you may have a cracked engine block. Conversely, if your car is exposed to freezing temperatures when there is not enough antifreeze in the cooling system, the engine block can crack. Aside from water in the oil, other signs of a cracked engine block include excessive engine smoke, overheating, and low engine compression.

Worn Piston Rings

When piston rings go, your car will start to consume oil excessively, often resulting in white, blue, or gray smoke emitted from the exhaust. Your engine may also overheat and have performance struggles when you go to accelerate.

Furthermore, when piston rings go wrong, they put added pressure on the crankcase. In turn, the engine seal becomes damaged, leading to oil and/or coolant leaks.

Cracked Cylinder Head

Not to be confused with a blown head gasket, a cracked cylinder head deals with the piece of metal that seals the cylinders within the engine block. The head will contain valves, and camshafts (occasionally), and enable air and fuel to enter the engine for combustion. Cracked cylinder heads and blown head gaskets often exhibit the same symptoms, such as white smoke from the exhaust, rough running, overheating, combustion gases in the cooling system, and oil and coolant mixing.

Can You Drive With Water in the Engine Oil?

It depends on the quality of the engine oil. If the consistency is not milky or frothy, then there is only a minimal amount of water, driving should be safe. Let your car sit for a bit. The water may burn off naturally.

That being said, driving around with water in your engine oil is risky. Your best option is to take the vehicle to a qualified mechanic as soon as possible. They may be able to find an issue that you were unaware of, preventing any further damages from occurring.

Final Thoughts on Water in Engine Oil

What happens when water mixes with oil in the engine? Nothing good. A little bit of water is not problematic and sometimes happens naturally. However, there could be issues with your PCV system or your engine that have caused water or coolant to mix with your motor oil. You do not want to drive around with the possibility of a blown head gasket, cracked engine block, or other issues. Go to a mechanic as soon as you can for repairs.