Engine Sludge Symptoms, Causes, And How To Fix The Problem!

Engine Sludge Symptoms, Causes, And How To Fix The Problem!

March 26, 2023 0 By CarGuy

Are you thinking that there is sludge in your engine and you are asking yourself about the engine sludge symptoms? Well, if that is the case, then you are in the right place. Because in this article, there will be a lot to cover.

Doing a proper research on a problem is always a smart thing to do. You just don’t want to leave things to chance and end up paying really hefty repair bills. Car mechanics do not take the oil sludge problem seriously, they will just change the oil and call it a day.

But the reality is a lot different when you have a problem with oil sludge in your engine. We are saying this because if the engine is not properly cleaned with a special solution, your engine will still suffer from oil sludge. And sometimes these solutions do not help at all and you will eventually have to disassemble the engine and completely rebuild it since the oil passageways can get completely clogged up.

In this article, we are going to try to help you out. First, we are going to learn what is the engine sludge meaning and learn more about this problem, then, we will learn if this problem is really bad and also the main causes for this sludge. Once we clear the causes, we will cover the engine sludge symptoms and learn what are the common symptoms associated with this problem and how you can tackle the problem out. So, if you want to learn more, follow along.

Engine Sludge Meaning

Now let’s discuss more about the basics. More specifically the engine sludge meaning. We think that we need to cover this topic because there are a lot of beginners who are suffering from similar issues and do not know what are these concepts.

So, what is engine sludge? Well, engine sludge is basically referring to gel-like or semi-solid deposits that are found in your engine oil.

As you can tell, the oil can get thicker and resemble a sludge, or there could be semi-solid chunks of these deposits in your engine oil.

This is the result of contaminated engine oil. Engine oil as you know is a greasy substance with equal viscosity. When the engine oil is new, it has a light brown color and is relatively thin, when the engine gets hot, the oil is even thinner. And that’s how oil should be.

So, if your engine oil gets black and thick, and has chunks of debris inside, then you have an engine sludge problem. And this is basically one of the engine sludge symptoms. The visual representation of a problem.

But don’t worry, later on, we are going to cover all of the engine sludge symptoms. Now let’s move on and see if this engine sludge is bad or not.

Is Engine Sludge Bad

Now that we cleared the engine sludge meaning and learned what this problem is all about. We can slowly move on to other topics and learn if this engine sludge is bad or not. Is it bad or you can live with it?

Well, the short answer is yes, it is bad. In fact, it is a clear problem that you need to sort out in order to have your engine back in top shape.

Because if you don’t care about your engine and you leave it like that, you risk having your engine totaled.

What is worth noting is that this is a common thing on old-school pushrod engines and less of a problem on modern engines.

Mainly because newer engines use better quality oil with washing detergents that remove sludge and debris. But if you have an old-school engine like a Chevy 350, or a Dodge 440, this is a normal thing. So, you should not panic if you notice this problem in your car.

Some engines are even more prone to developing sludge than other engines because of their design. The oil passageways are too thin and they clog up easily, especially when using mineral oils.

Still, whenever you notice sludge, you should at least do some quick oil changes in order to make sure that most of the sludge is gone. But more on how to get rid of the problem, we will cover later on.

What are the exact causes of this problem with oil sludge in your engine? Let’s elaborate more on that in the following chapters.

What Causes Engine Sludge

Now before we dive into the engine sludge symptoms, let’s cover the causes of this problem in your engine. As you probably know, there could be more than a few issues that could trigger the engine sludge problem. So, let’s cover them thoroughly and learn more about these causes.

1. Poor Maintenance

The first cause for the engine sludge and the appearance of engine sludge symptoms is poor maintenance. So, what this means?

Well, if you neglect your engine and do not maintain it well, you will have some oil sludge issues. And this will be present for any engine.

Engines do not tolerate when you neglect them, so with each delayed oil change, you will be left with burnt oil. And this oil basically sticks to the oil passageways around the engine. And this debris will eventually completely clog up your engine.

This is why regular maintenance is key when it comes to avoiding this problem and avoiding experiencing engine sludge symptoms.

You should follow the intervals for the engine oil. And do not forget that you should always use quality engine oil. Modern engines require using fully-synthetic oil. And you should use this type unless you want some problems like these to occur.

2. Poor Engine Design

The second very common reason that can cause sludge and engine sludge symptoms is poor engine design.

Over the years, engine design evolved quite a bit and solved most of these problems. So, older engines are generally more prone to develop sludge.
If you run a pushrod engine from the older generations, then you can expect oil sludge development to occur more often than on modern engines.

This is why the best idea is to follow the times and purchase something more refined with fewer miles if you don’t want to deal with problems like these.

Common engines that suffer from sludge are as we mentioned, the old-school pushrod engines. But it can also be common in some Ford engines like the 5.4 3v or some of the older Toyota engines. Now let’s continue with the next engine sludge causes before we cover the engine sludge symptoms.

3. Oil Contamination

The next cause that we are going to cover before we learn about the engine sludge symptoms is oil contamination. And honestly, oil contamination is a serious problem.

Oil can be contaminated in multiple ways and you will end up with a sludge inside of your engine. For example, the car could have a bad oil pan gasket and be submerged under water, and water to enter the engine.

But the most common way of oil contamination is from the coolant. If your engine blew a head gasket, there could be some leaks. These leaks will go from the engine coolant compartment to the oil compartment. And eventually creating a big sludge from your engine oil.

This is why it is a good idea to check your engine oil and make sure that the engine oil is in good condition and you don’t have oil mixing with coolant.

Another way for the engine oil to contaminate is metal contamination. Where metallic particles from the engine internals combine with the oil and cause it to thicken up. This happens on extremely worn-out engines. And also, there is the chance of gasket material also to thicken up the engine oil. But what are the engine sludge symptoms? More about the symptoms, we are going to elaborate in a bit.

4. Low Oil Level

The next probable cause for engine oil sludge symptoms is the oil level. For example, if you run the engine low on oil, the engine oil will cook off much sooner.

Engine Sludge Symptoms

And when the oil gets burnt, it will start to create sludge deposits that will stick to the engine block and cause sludge.

This is why we advise that you monitor the engine oil level. As well as the condition of the oil in order to avoid these things from happening to your vehicle and suffering from engine sludge symptoms.

5. Bad PCV Valve

And the last cause of the engine sludge is the bad PCV valve. So, what is a PCV valve? Well, this valve is a part of the positive crankcase ventilation system.

In general, when the engine is spinning it starts to create gases inside the crankcase. So, these gases have to go somewhere. And in order for the engine to avoid damage, the PCV system was invented.

This system is really simple. It has a PCV valve that works with the help of a vacuum. When the right amount of gases is met, the PCV valve opens and purges the gases.

The PCV valve is usually mounted on top of the valve cover and from there it is connected with a hose to the intake manifold. So, when it opens, the gases are sent to the intake manifold and then into the combustion chamber to burn off.

What can happen is that sometimes these PCV valves can get clogged up. And when they are clogged up, they will start to create problems inside the engine. Engine sludge is common, as well as overall poor engine work. The engine can also blow some seals.

Especially the valve cover gasket fails more often since the gases have to escape from somewhere. But what about the engine sludge symptoms? More on the symptoms, we are going to cover next.

Engine Sludge Symptoms

So, we covered the engine sludge causes. Now let’s take a look at the engine sludge symptoms and learn more about the most common symptoms associated with this problem.

Knowing the symptoms is really useful because you will be able to tell if you have sludge or not. So, let’s cover them in the following chapters.

1. Oil Light On

The first in our list of engine sludge symptoms is the engine oil light on. So, why is this the case? Well, in your engine, there is a special sensor known as an oil pressure sensor, some people call it oil sending unit.

It basically does the same thing, it measures the oil pressure in the engine and detects abnormal processes. Like high or low oil pressure, and high or low oil level.

Engine Sludge Symptoms

So, when this sensor detects a problem, it will trigger the oil light to turn on. And is really important to act quickly in these cases. Since the oil light isn’t there for no reason. The oil light turns on in these types of situations.

So, checking the engine oil and its condition is mandatory. Now let’s move on to the next engine sludge symptoms.

2. High Oil Pressure Readings

And the next in our list of engine sludge symptoms is precisely what you need besides the oil light that we listed above.

When you have only the oil light on, you don’t know what is exactly happening. But if you check the oil pressure gauge, you will see if you have a problem with your engine oil and if there is sludge.

A good oil pressure reading is somewhere between 20 and 60 PSI. So, if the PSI is constantly close to 60 or above 60, then you have sludge and this causes the oil pressure to rise.
The oil passageways are clogged up and you are left with an engine that is not lubricating properly. And this will lead to imminent engine failure. That’s why it is important that you sort out the problem before it is too late. Now let’s move on to the next engine oil sludge symptoms.

3. Engine Oil Is Thick

The next symptom on our list of oil sludge symptoms is the situation when you have thick engine oil. And this is one of the most common symptoms associated with the problem that alerts people that they have sludge in their oil.

When they decide to change the oil, they notice that the oil leaks really slowly from the drain bolt and is all black. This is a clear sign that you have oil sludge inside your engine.

Engine oil should not be sludgy. It is evident that you pushed the engine oil too far and it simply burnt out and this oil simply doesn’t do its job anymore.

Or if you notice a change of color and the engine oil is thick and has a milkshake consistency, this could also mean that the coolant and the oil are mixed together and are causing this problem. Watch out for these two situations. Now let’s continue with the next engine sludge symptoms.

4. Overheating Engine

Next in our list of symptoms is the situation when your engine overheats. And this will be quite common if you have serious oil sludge in your engine.

Oil flow should be constant and you should have a proper flow of oil all of the time. If there are obstructions in the oil passageways, you will have an overheating engine.

Engine oil not only that it lubricates the engine, but it also dissipates the heat from the block. And if the oil is stopped from flowing, you will have an overheated engine. Now let’s continue with the next engine sludge symptoms.

5. Poor Fuel Economy

Another common symptom in our list of engine sludge symptoms is poor fuel economy. This is expected since the engine has hot spots.

Engine Oil Sludge Symptoms

When an engine has hot spots, it doesn’t operate anymore as the way it should and you will also have worsened fuel efficiency. So, if the MPG hits rock bottom, something clearly is going on inside your engine.

6. Noisy Engine

And the last symptom in our list of engine sludge symptoms is the noisy engine. The engine will be very noisy if there is no proper lubrication.

Metal-to-metal contact is imminent, along with the heat that will be created. And this noise will soon turn into a rod knock. And eventually, your engine will either seize or spin a bearing. This is one of the sad outcomes of excessive oil sludge that you probably don’t want to experience.

And now that we cleared the engine sludge symptoms, let’s move on to the removal process and learn how you can clean your engine from this sludge.

Engine Sludge Remover

Now that we covered the engine sludge symptoms, we can move on and learn more about how you can de-sludge your engine.

For this purpose, you can try Seafoam as many other people do. Or you can flush the engine oil with a special oil by BG Dynamic.

This oil has special detergents in it that will remove most, if not all oil contaminants in your engine. So, we think that you should give it a try. More on the whole process, in the video above.

Overall, all you need to do is to flush the engine oil with the BG Dynamic product and then run the engine for 45 minutes at a certain RPM. And this will remove the sludge from your engine. So, we learned the engine sludge symptoms and how to remove engine sludge, now let’s discuss the costs in the following chapter.

Engine Sludge Removal Cost

The engine sludge removal if you are using a solution is nothing too crazy. Only a few hundred dollars in the worst-case scenario.

But if this doesn’t help and you have to refurbish the engine, then things might get too expensive. A rebuild in the best-case scenario can cost you $2,500. And sometimes in these cases, a new engine might sound like a smarter idea than rebuilding the old one.


In this article, we have covered quite a bit when it comes to the engine sludge problem. We learned what is engine sludge and whether or not this is a big issue for your engine.

Then, we discussed the causes of engine sludge, as well as the engine sludge symptoms. After that, we moved on to solving this problem with a special solution, and also we discussed how much will it cost you to fix the problem.



How Do I Know If My Engine Has Sludge

The simplest way to find out that your engine struggles with oil sludge is to remove the valve covers. If there is sludge in the engine, the valves will be covered with this sludge. Also, you can drop the oil pan in this situation, and inside the oil pan, there will also be a ton of sludge. In addition to this, the condition of the engine oil can tell a story. If the oil is very thick and black, this means that you have sludge.

Can Engine Sludge Be Fixed

Yes, there are some detergents that are sold at car parts stores that do this work, you just flush the engine with this solution a few times and most of the sludge will disappear. You can also do a few quick oil flushes if the problem is not very serious. Flushing the oil will remove most of the sludge if it’s done quickly.

What Are The Effects Of Oil Sludge In Engine

Having oil sludge means that your engine is not properly lubricated. Your engine will have increased wear. Especially the rod bearings and piston rings. If the car is driven for a long time like this, it could lead to a situation known as a rod knock. When rods start knocking, you need a new engine.

Can Oil Sludge Cause Engine Failure

Yes, oil sludge can lead to engine failure. This is the case because engine oil will not lubricate the engine and also will not dissipate the heat. When this happens, premature engine wear will occur and you will have a serious problem. You will highly likely have to rebuild or replace the engine with a new one.