Do you know the difference between clean and dirty engine oil? By color, you probably do. But what about the other factors? See, engine oil contains a number of additives, like detergents and anti-corrosives, to keep the engine lubricated for about 5,000-7,500 miles or 3-12 months. Every time you use your vehicle, however, the engine oil gets dirtier and starts to lose its functionality. Normal use and extreme temperatures will cause reactions to occur within the oil, turning it thicker and more sludgy.

Once the oil becomes too dirty, it will impact the performance of your vehicle and may also lead to serious complications. To help you decide whether you are dealing with clean vs dirty engine oil, here are a couple of differences to know.

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Key Differences Between Clean vs Dirty Engine Oil

Here are the four ways you tell the difference between clean and dirty motor oil:


One of the most reliable ways to tell clean vs dirty engine oil apart is to look at the color. Simply remove the dipstick from the engine and look at it. Clean engine oil is typically pale yellow or amber in color, kind of like an amber ale. Once it starts getting run through the engine and filter, the amber color begins to darken to brown or black. The dirtier the oil, the darker it becomes.

This video shows you just how disgusting old, dirty oil can become:


The next way to test just how dirty your motor oil has become is to touch it. Put a little bit of the oil on a finger and rub it. A smooth texture like getting olive oil or pizza oil on your hand indicates fresh oil. If the oil is dark and gritty, it is dirty. That grit you feel is any number of impurities, which are mentioned further below.


You can also tell the difference between dirty vs clean engine oil by checking the viscosity. When talking about viscosity, we are discussing the thickness of the oil. There is a range of viscosity ratings, so it is vital to know the right one for your vehicle. Viscosity affects how the oil performs at various temperatures. As oil gets dirtier, the viscosity may change, becoming thicker and stickier, thereby impacting the performance of your car, truck, or SUV.


Engine oil will collect impurities over time, like dirt, dust, metal shavings, and other debris. Other contaminants, such as carbon and fuel deposits, may also form. Impurities gather naturally, but it is a sign that your engine oil and oil filter will need to be changed sometime soon. If those contaminants continue to cycle through the engine for much longer, it can cause accelerated wear and tear to the moving parts.

How Do You Know When Your Engine Oil is Dirty?

Aside from looking directly at the oil in your car by way of the dipstick, there are a couple of symptoms that result from driving around with dirty engine oil:

  1. You may hear knocking sounds coming from the engine, a sign that the pistons have been worn down due to damage from dirty engine oil.
  2. Smoky exhaust. When you start seeing more exhaust that is no longer barely visible but black, it could be a sign that your oil is dirty and starting to burn instead of lubricate.

How to Prevent Engine Oil From Getting Dirty

There truly is no way to keep your motor oil from getting grimy. It happens, because that is what it is meant for. However, you do want to avoid using dirty engine oil for too long.

Here are some ways to prevent driving around with dirty engine oil:

  • Regular maintenance. If you are concerned about clean vs dirty engine oil, then be sure to change your engine oil regularly. 3,000 miles for conventional oil. 5,000 to 7,500 for synthetic oil. Some cars have manufacturer recommendations of around 10,000-15,000 miles these days, so consider how often you use your car and what kind of conditions it is subjected to, as that will help you decide the interval.
  • Use an engine sludge remover. This product will reduce the amount of dirt and grime in the engine, keeping your oil fresher for longer.
  • Avoid stop-and-go driving. Short commutes are worse for your vehicle than longer ones.


When it comes to clean vs dirty engine oil, the key takeaway is that dirty oil looks and feels dirty. You don’t want that in the engine of your vehicle for too long, so get it changed out as soon as possible. Keep an eye on the performance of your car, too. That will tell you how dirty your engine oil has become. And, as always, stay on top of routine maintenance.

Categories: Oil Guides


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