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Black Smoke From Exhaust—Engine Burning Oil

I've worked in a variety of hands-on professions and love to write about topics that can save readers from needless expenses.

Black smoke from exhaust pipes can be easily corrected in most cases by changing the weight of oil you use.

Black smoke from exhaust pipes can be easily corrected in most cases by changing the weight of oil you use.

What Causes Black Smoke From Exhaust Pipes?

As engines begin to age and wear out, they begin to change. They still work fine, but they aren't quite as efficient or powerful as they once were. Most older engines run hotter. This causes excess emissions begin to seep out of the exhaust pipe.

At first, these emissions aren't visible to the naked eye, but as time goes on, black smoke generally begins to emanate from the exhaust pipe, carrying with it the scent of something burning that isn't supposed to be.

So what is this black smoke from the exhaust pipe? Truly black smoke can be unburnt fuel that's forced out of the exhaust system, but usually it's oil, which is more commonly labeled blue smoke. What I'm calling black smoke in this article, most technically should be labeled blue smoke, because truly black smoke is unburnt fuel from a leaky fuel injector, poor oxygenation in the fuel/air mixture, or carburetor malfunction.

So how can you be sure? One easy way to know if your engine is burning oil, or if the black smoke is caused by something else, is to check your oil levels. If your oil is steadily consumed while you drive, then you know your engine is burning oil. If not, then your black smoke is most likely from unburnt fuel being forced out of the exhaust.

Here's how it works. Motor oil is used to lubricate the inner workings of your internal combustion engine, the metal pistons and rods and moving pieces that all sit in close contact with one another. For many tens of thousands of miles, the standard 10w30 oil does its job and the car is lubricated.

But all the while, the metal pieces are slowly beginning to wear down, creating a greater gap between the moving metal parts. Once this gap gets large enough, oil can begin seeping into your combustion chamber, causing your engine to start burning oil.

Different Oil Weights

The good news is that engines burning oil isn't a new problem. This has existed for quite some time. And solutions are in place to help keep that black smoke out of your exhaust system. This is the reason why different types or weights of oil exist.

When you see an oil labeled 10w30, it tells you two things about the oil. One is the weight, or thickness of the oil. The other is the viscosity, or flow rate of the oil. Low weight and viscosity oils like 5w30 and 10w30 are perfect for newer vehicles whose machined precision parts are functioning with little internal wear and tear.

But for older engines, which need a thicker oil and flows more slowly, a higher weight and viscosity oil will probably be needed. Here are a few oils that might be good to switch to if 10w30 isn't working well for you anymore.

Check with your mechanic about the best oil for your car.

Check with your mechanic about the best oil for your car.


10w40 oil is sometimes a great switch if your engine is beginning to burn oil. The oil is just a bit thicker and can help prevent minor amounts of oil seepage into the combustion chamber.

Most people who are running 10w30 and are starting to experience oil consumption like to first switch to 10w40, especially if they're living in a colder climate. In a year-round temperate climate, many people just use a straight weight oil like SAE 30, which we discuss below.

10w40 helps keep the engine protected while running at cold operating temperatures, but doesn't flow as heavily as 10w30, keeping it from seeping into the combustion chamber. The next time you go in for an oil change, talk to your mechanic about switching to 10w40 and see what they think of the idea.

SAE 30

Another option is to go to a straight weight oil that acts the same in high and low temps. Because an engine is cold when it starts and hot when it warms up, oils can have different properties depending on what temperature they're at.

If you're needing a thicker oil and you live in a warm climate, or if you live in a cold climate but want to use a thicker oil during the summer, then SAE 30 might be the right way to go for you. Since your engine isn't ever getting really cold, you don't have to worry about damage occurring until the engine heats up.

But if you're going to go this route, you should talk to your oil change professional before making this leap to get their advice. If SAE 30 is used improperly, it can cause serious internal damage to your engine.

No more smoke. Problem solved!

No more smoke. Problem solved!

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.