Water in engine oil symptoms, causes, best test method in 3 steps with a possible temporary fix to get you back driving again quickly.
This article will discuss what water in engine oil is, how it affects your car, and how you can prevent it from happening. By understanding this issue, you can take steps to ensure your car runs smoothly and lasts longer.
In This Article
The Culprits Behind Water Contamination of Engine Oil
Water contamination in engine oil is a serious issue that can cause significant damage to your car engine. It occurs when coolant from the radiator leaks into the oil leading to a contaminated mixture that can cause serious damage to the engine. It also occurs when condensation builds up inside the car engine resulting in oil tarnish and sludge buildup.
What Happens When Water Mixes With Oil in Engine?
The most common signs of water contamination include difficulty starting, a decrease in power, an increase in engine noise, white smoke from the exhaust pipe, and milky-colored oil on the dipstick or under the oil cap. This water can cause issues with your car’s engine performance. In addition to that, water accumulation can lead to oil sludging formation and ultimately wear and tear on your engine. If you notice any of these symptoms, it is important to take action quickly to prevent overheating and further damage.
How to Diagnose and Fix Water in Engine Oil
The engine oil dipstick and under the engine oil cap are quick and easy ways to check for water in engine oil symptoms. If you look under the engine oil filler cap and on the engine oil dipstick for a white milky appearance similar to a creamy chocolate milkshake it indicates internal engine problems like a blown head gasket. When you remove the drain plug (sump plug) from the oil pan (oil sump) the water will flow out first because water is denser than oil.
Testing for a Blown Head Gasket
A coolant tester is a quick and simple way to check for leaking exhaust gases into the engine cooling system caused by a blown head gasket, cylinder head crack, or engine block crack. With the head gasket sealing the bottom half of the engine which has the pistons and piston rings with the top half of the engine which has the valves is a bit like the meat in the sandwich. Its 3 main functions are to seal water, oil, and compression.
Here you can check out the best Combustion Leak Detectors, often called Block Testers, how to use one, and what to look out for when you want to purchase one.
Before buying a Combustion Leak Detector, double-check that it comes with the necessary test fluid and a sturdy case to prevent any potential damage caused by mishandling. With a comprehensive Block Tester Kit, you’ll no longer need any extra components; it’s ready to be used out of the box. It contains enough test fluid for about 16 tests and additional bottles are also available if needed.
Block Tester Kits are incredibly valuable when it comes to buying a used car too. You can use them to find out if the vehicle has any problems and avoid buying someone else’s problem that could cost you thousands of dollars in repairs. Plus, they make it simple and easy to check for a defective head gasket.
As seen in the video block testers are used to detect combustion gases in water-cooled engines, such as petrol, diesel, and LPG. They work by changing the color of the blue liquid it contains to yellow when combustion gases are present. This can alert you to potential problems with the cooling system quickly and efficiently.
If you notice a decrease in the coolant levels of your vehicle, it may be due to a combustion leak. The block tester can help diagnose this issue accurately so that you know what needs to be done next. Whether you need to repair the car or try using a head gasket repair, the block tester will set you on the right path.
Before testing the coolant, drain some out from the radiator to avoid any potential contamination of the test fluid.
- Place the block tester into the radiator so that it fits snugly.
- Squeeze the bulb to check if the testing liquid changes its color from blue to yellow.
- A transition from blue to yellow in the fluid is a sign of a combustion leak.
Suppose you’re testing other combustion engines or generators. In that case, it’s handy to have a tool in your garage or tool kit that works on any internal combustion engine with a closed cooling system.

You Can Have Oil In Water Too
Motor oil in water is usually a bigger problem when it comes to cleaning the sludge from the engine cooling system and radiator. When you open the cooling system cap or radiator cap have a look for oil in the water and around the cap. Also, beware of any quick fixes like the owner or seller using automotive additives or head gasket sealers. These work like magic in many cases but they are a quick fix.
A Bad Oil Cooler
Oil coolers are relatively uncommon in cars that run on gas engines. However, they are a mainstay of turbocharged vehicles. Leaks from an oil cooler may cause oil to mix with coolant, which would be an indicator of a problem. When oil cooler leaks occur, many people tend to assume that the head gasket is blown. However, the engine generally functions normally in such a situation. A damaged head gasket will usually cause the engine performance to become affected. If an oil cooler is leaking, it’s a relatively inexpensive repair job. The replacement parts – the oil cooler and its gasket – need to be installed, and then the cooling system is flushed and refilled.
Leak in the Transmission Cooler
Some cars with an automatic transmission have a dedicated transmission fluid cooler that is typically connected to the radiator. Over time, cracks may form between the two parts, leading to transmission fluid leaking into the coolant system. The coolant can look pink and foamy, which is an indication of a problem. Unfortunately, it might also reach your transmission and eventually cause irreparable damage, requiring a replacement.
Preventative Maintenance Tips to Reduce the Risk of Water Contamination
An engine oil change is crucial because there are a lot of additives in the oil that become dirty and essentially wear out causing the lubricating properties that protect the engine to diminish. This results in some metal parts being eaten away and water being retained in the crankcase which results in sludge.
The sludge mixture will just keep building up by attracting more abrasive particles and then wear down the engine instead of protecting it as clean oil does. This is why changing your oil at specified intervals and more frequently than the manufactures recommendations if you drive less frequently or in abnormal conditions like stop-start traffic is so important.
Oil Change Replaces:
- detergents
- dispersant additives
If your vehicle is used a lot for short trips and doesn’t reach operating temperature often before you turn the engine off then it is advisable to change the oil more frequently than what the manufacturer recommends to get the most out of your engine and protect moving parts.
When do I need to get my car’s oil changed? You should have your car’s oil changed every 3,000 miles or about six months.
For general driving of the vehicle, every 5,000 kilometers or 3,000 miles (6 months) is a good rule of thumb before you need to change the engine oil.
Non-Synthetic Oil Change Interval
For older cars using non-synthetics, say no more than every 5,000 kilometers or 3,000 miles. (6 months)
Synthetic Oil Change Interval
With more advanced engine designs and better oil formulations like full synthetics, manufacturers are always increasing the oil-change intervals. It is still highly recommended to check the oil yourself frequently and has it changed more regularly too. With newer cars say no more than every 10,000 kilometers or 6,000 miles (12 months) just to be on the safe side.