Dirty Engine Oil Symptoms — Top 6 Possible Red Flags

Like nothing is immortal in this world, so is the engine oil. It ultimately gets dirty, which I call “dead” engine oil; you can name it anything you want. It must be replaced promptly to keep your vehicle’s internal working in good condition.

Most of the drivers solely rely on the mileage as an indicator to replace the engine oil, and I’m not an exception in this case. However, factors such as engine oil quality, car’s age, and driving tactics also play a key role in determining dirty-oil-change date. 

Although you can check it by pulling the dipstick out and seeing the changed color, there are many other symptoms as well. I’ll tell you all those symptoms in this detailed guide, along with the causes and a step-by-step process to change it yourself.

What Is Dirty Engine Oil? What Does It Mean?

Engine oil serves two purposes. First, it keeps the engine’s moving components lubricated so they can rotate, shift, and/or move smoothly with minimum friction. Secondly, it acts as a courier that carries debris and contaminants away. 

Dirty engine oil means that the oil in your car’s engine is no longer clean and has become contaminated with various particles such as dirt, dust, metal shavings, and other debris. It can no longer provide the needed lubrication. 

Dirty Engine Oil Symptoms | How To See Engine Oil Is Dirty?


Engine Warning Lights

The “oil light” on a car’s dashboard is the first indication of dirty engine oil. If it is blinking, it means something has gone wrong with the engine oil in your car. Most probably, it has become dirty. It can also indicate a lower oil level in the compartment. 

Engine Noise And Knocking

As I have told you earlier in this guide, engine oil lubricates the engine’s parts so they can move freely without any friction. In short, engine oil ensures that there is no metal-to-metal brushing so the noise. 

As the oil becomes contaminated with dirt and debris, it loses its lubricating properties. With lesser lubrication, there is more friction, so the engine noise. In severe cases, you could hear rumbling or knocking sounds.

Dark, Dirty Oil

When fresh, clean oil is poured into the car’s engine, it is golden-brown/amber, a bit like honey. Once it turns bad or dirty, its color changes and becomes even darker. In severe cases, it is totally black. TIP: I check my car’s engine oil once a month if I drive her regularly. 

Burning Oil Smell

Is there a burning engine oil smell inside your car? I’m sure it is due to dirty engine oil. Let me guess! It happens every time you start the car’s engine; your nose can catch some unusual smell that wasn’t there before. Right? 

If your engine oil has not been changed for an extended period, it can break down and lose its lubrication properties. This can lead the way to overheating, which can cause the oil to burn and produce a strong smell.

Exhaust Smoke

Suppose you have seen the above dirty engine oil symptoms for a few weeks now and haven’t changed it. If you do so, the last milestone for your car’s engine, in such a case, is to start releasing smoke from the tailpipe. This is the end of your car’s dirty engine oil.

How To Confirm Engine Oil Is Dirty?


You might be a curious person who might want to know how I personally react if I see any of the above-mentioned signs of dirty engine oil. Well, honestly, nothing special! My first priority is to confirm if engine oil is the real reason behind it. 

To confirm the engine oil is genuinely dirty, I locate the oil dipstick to access and assess the engine oil to see its color. The oil dipstick is generally located near the engine’s bottom, near the oil pan. It is a long, thin rod with a handle on one end.

I follow these steps to check the oil and suggest you do the same. 

  1. Park your vehicle on a level surface.
  2. Turn off the vehicle’s engine and allow it to cool down for a few minutes.
  3. Find out the oil dipstick.
  4. Remove the oil dipstick from the engine.
  5. Clean the oil dipstick with the help of a rag.
  6. Insert the oil dipstick back into the engine.
  7. Remove the oil dipstick again.
  8. Check the color of the oil.

Clean engine oil is generally amber or light brown in color. As it gets dirtier, it becomes darker and more opaque. In the worst cases, it is totally black. If the oil is black or dark brown, it is dirty and needs to be changed immediately. 

What Causes Engine Oil To Get Dirty Quickly?


The essential element that keeps the engine operating properly is engine oil. However, a number of engine problems could negatively impact how well it performs. 

In my experience with the dirty oil from my previous car, the following were the causes and reasons for the engine oil getting dirty quickly.

Overheating Engine — A car’s normal engine temperature is about 190 to 225 degrees Fahrenheit. Excessive heat affects lubrication and viscosity by causing oil molecules to break down. 

Enhanced Oxidation — Oxidation is a natural process that occurs within an engine. Over time, it intensifies and contributes to the chemical breakdown of engine oil. This reduces its lubricating effectiveness and necessitates regular oil changes.

Coolant Leak — If there’s a coolant leak in the engine, it can mix with the oil. Coolant contamination can give the oil a milky appearance and reduce its lubricating effectiveness. 

What To Do With Dirty Engine Oil? How to Change It?

Well, the ultimate solution to dirty engine oil is to replace it with a new, clean, fresh engine oil. But before that, cleaning the dirty oil is essential. This is how to do this at home.

Drain the Old, Dirty Oil. Firstly, remove the oil cap and loosen the drain plug on the oil pan. Once the oil drains out, put back the drain plug and remove the old oil filter.

Add the Cleaning Solution. How to clean dirty engine oil? Pour the engine cleaning solution into the oil reservoir, which is located where you pour new oil. 

Let the Cleaning Solution Sit. Leave the solution in your engine for a recommended amount of time to let it break down and dissolve the sludge, grime, and other contaminants.

Drain the Solution. Drain the solution from the oil reservoir, which will contain dirt and grime.

Install a New Filter. Install a new oil filter, as the old one has likely captured dirt particles and contaminants from the old oil.

Add New Engine Oil. Pour new, clean oil into the engine. Don’t forget to see your owner’s manual for the suggested oil type and amount.

Start the Engine. Start your vehicle’s engine and allow it to run for a few minutes to make sure the new oil circulates accurately and has no leaks.

How Often Should You Change Engine Oil?


If you own an old car, like me, you would probably need to change its engine oil every 3,000 miles or three months. However, those who have newer cars can drive their car for up to 6,000 miles before changing the oil (or after every six months).


Some of the possible signs of dirty engine oil include a blinking “oil light”, strange engine noises such as knocking or rumbling, a burning oil smell inside/near the car, or smoke coming out of the exhaust pipe. 

If you see any of the dirty engine oil symptoms, do a quick confirmation. Take the oil dipstick out of the engine, clean it with a rag, insert it back, and remove it again. If it has black/dark brown engine oil on it, it means your car’s engine is dirty. 

So, what to do next? The solution is simple: change your car’s engine oil. Drain the old engine oil, add a cleaning solution, let it sit there for a while, and then, drain it. Replace the old filter and pour new engine oil. 


What Happens When Engine Oil Is Dirty? 

When engine oil becomes dirty, it loses its effectiveness in lubricating and protecting the engine’s moving parts. It increases friction, excessive heat, and accelerated wear and tear on the components of the engine. 

What Are the Symptoms of Bad Engine Oil?

Bad or black engine oil symptoms include a burning oil smell, unusual engine noises (such as knocking or rumbling), engine warning lights on the dashboard, and smoke from the exhaust pipe. 

What Does Dirty Engine Oil Look Like When It Needs To Be Changed? 

Engine oil that needs to be changed may appear black/dark brown and dirty. It may have a thicker consistency and a gritty or sludgy texture. 

Additionally, the oil may have a burnt odor or contain visible particles, indicating that it has reached the end of its service life and requires replacement.

Does Dirty Oil Affect Acceleration? 

Yes, dirty oil can affect acceleration. As the oil becomes contaminated and loses its lubricating properties, it can increase friction between engine components. 

This added friction can hinder the smooth movement of parts, resulting in sluggish acceleration and reduced overall engine performance.