Oil Coming Out Of A Briggs And Stratton Carburetor? (Fix It Now!)

Nick Durante
by Nick Durante
Briggs and Stratton’s mowers are the gold standard, but that doesn’t mean that they always work ideally. Oil can seep from the carburetor for several reasons, such as a blown gasket. Whether it be a steep incline or mechanical problems, let’s explore what you can do when oil leaks from your Briggs and Stratton’s carburetor.

Briggs and Stratton are one of the leading names in lawnmowers, and they earned their reputation. As great as their mowers are, problems can still occur, and they can be quite frustrating. With that said, what causes oil to come out of the carburetor on your Briggs and Stratton mower?

If you mow at a steep incline or tip your mower on its side, it can cause the oil to come out of the carburetor. Leaking oil can also be a sign that your head gasket was blown, and that can cost you $300 at least to have repaired. A damaged carburetor float can also cause an oil leak, and it also happens when the air filter is oversaturated.

Don’t panic when oil comes out of your Briggs and Stratton carburetor, because there are many fixes. Let’s take a look at the most common causes and fixes for a carburetor oil leak on Briggs and Stratton mowers.

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Possible Causes

It’s important to diagnose what caused your carburetor to leak oil before you can fix it. Whether you tipped it on its side, you’ve blown a gasket, or the air filter is oversoaked, you’ve got a problem. Let’s take a look at some of the most common causes for oil coming out of the carburetor.

Tipped On Its Side

When your Briggs and Stratton mower is tipped on its side, oil can come out of the carburetor. Lawnmowers are more sensitive than they look, and even a 15-degree shift when tipped can cause the oil to leak. Unfortunately, 15 degrees is enough for the carburetor to point down and leak oil into the breather tube.

The easiest way for this to happen is to mow a lawn that has too much of a steep incline. Sometimes you can only find this out when it’s too late and the mower is already leaking oil. The other most common way that tipping causes oil leaks is when you are cleaning the blades and have them on their side.


In this case, the solution is to avoid mowing at steep inclines entirely so no oil leaks from the carburetor. Unless you have one of the best zero-turn mowers, you should never mow at an incline. When it comes to cleaning your mower, never tip it on its side when you’re cleaning the blades to avoid leaking oil.

You can safely clean your mower by tilting the air filter upwards so that there is no leak. That way, you won’t run the risk of oil leaking out of the carburetor.

Blown Head Gasket

A blown head gasket is the most expensive and damaging cause of oil coming out of your carburetor. Briggs and Stratton make great parts, but head gaskets can still blow out even if it is not your fault. However, the most common cause of a head gasket blowing out is that the mower is overheated from too much use.

Too much heat leads to expansion inside of the Briggs and Stratton mower, and that can blow the head gasket. You’ll generally notice the oil leak before you even go to start the mower once a head gasket has blown out. Otherwise, you’ll be able to tell when you go to start it and the mower doesn’t start or stops working while mowing.


Sadly, the only fix for a blown head gasket is a full repair and part replacement. Head gaskets can be repaired or replaced for as little as $300, or as much as $1,200 for riding mowers. You could replace the head gasket on your own for less than $90, but it is recommended that professionals do it for you.

Air Filter

Oil and gas can leak out of the air filter on a Briggs and Stratton lawnmower, and it’s a common problem. You have to have a small amount of oil on your air filter in your lawnmower, but too much is a bad thing. Once the air filter has too much oil on it, the oil can drip and eventually get caught in the carburetor.

Otherwise, the oil could drip into the filter box and eventually leak out on its own anyway. It may take some experimentation to see how much is too much when it comes to oil on your air filter. The lack of oil on your air filter will make it so that dust particles can flow throughout the inside of the mower.


When the air filter becomes soaked in oil, you’ll need to squeeze it out like a washcloth. Once you’ve squeezed the excess oil out of the filter, you can place the air filter back into the lawnmower. Before you can run the mower again, you’ll need to clean out the carburetor to get the rest of the oil out.

Carburetor Float

A carburetor float is an essential part of the carburetor and the entire Briggs and Stratton mower. The float is responsible for the flow of fuel into the engine on a lawnmower, and it’s at the core of some oil leaks. Excess oil or fuel can leave behind a residue that causes the carburetor to float to work improperly and cause potential damage.

This can lead to both oil and gasoline leaking out of your Briggs and Stratton mower, and both are damaging. When your carburetor has a backflow of oil and fuel, it will leak out and work its way throughout the mower. You can avoid this by making sure to not allow old fuel to sit inside your mower for too long so that it doesn’t thicken up.


You will need to purchase a carburetor repair kit from Briggs and Stratton to fix this problem. They are available for between $9 and $30, and they are easy to use if you follow their directions. Even still, it is wise to purchase the kit and bring it to a professional as working with a carburetor is quite difficult and time-consuming.

Bring your mower to a small engine specialist because they have fair labor rates and lots of experience. Most small engine specialists won’t charge you more than $20 per hour for labor. Purchasing a carburetor repair kit on your own can also save you on the markup of parts.


A crankcase breather is a critical part of your lawnmower, and it helps alleviate pressure inside. Most crankcases can’t take more than 1 quart of oil, and any more than that creates a problem. The only place for excess oil to wind up is either in the carburetor, air filter, or cylinder.

You’ll notice right away that the engine on your Briggs and Stratton mower is not working ideally. If that’s not enough, the presence of leaked oil can tell you that it could be that your crankcase is overfilled. An overfilled crankcase can be dangerous, but it can most certainly cause your mower to operate below its full potential.


Keep a dipstick on hand so that you can keep an eye on your oil level in your crankcase. Stagger your pours when you add oil to the crankcase so that you don’t cause it to overflow. Check the oil levels with your dipstick as you pour oil into the crankcase so that you don’t exceed 1 quart.

Related Questions

How do I know if my crankcase is bad?

The easiest way to tell if your crankcase is bad if oil spills out of the carburetor. You can also tell that your crankcase is bad if your engine is not performing as powerfully as it was at first. Trouble accelerating or decelerating can tell you that your crankcase has gone bad, and spilled oil will tell you for sure.

What oil is used in a Briggs and Stratton?

Briggs and Stratton recommend that you use SAE 30W Oil for all of their lawnmowers. This is a high-performance oil that needs to be kept above 40 degrees Fahrenheit for optimal function. Fill your Briggs and Stratton mower slowly and check the level with a dipstick so that you don’t overfill it.

How does a Briggs and Stratton carburetor work?

Briggs and Stratton’s carburetors work by adding air to the gasoline before it enters the engine. The amount of gas and air depends on the speed and engine setting on your Briggs and Stratton mower. Carburetors have diaphragms that help to control how the air is added to the gasoline for even distribution.

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What Did We Learn?

If the oil is coming out of your Briggs and Stratton carburetor it could be because you have a blown head gasket. You can have a head gasket repaired and replaced for $300, or up to $1,200 for push mowers from Briggs and Stratton. Air filters become oversaturated with oil and that can lead to oil coming out of the carburetor.

Tipping your mower on its side is the most common cause of oil coming out of the carburetor. Avoid mowing at inclines or leaning it on the side of the carburetor when you clean your mower. Oil coming out of the carburetor is not a death sentence, but you should diagnose the problem and fix it.

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Nick Durante
Nick Durante

Nick Durante is a professional writer with a primary focus on home improvement. When he is not writing about home improvement or taking on projects around the house, he likes to read and create art. He is always looking towards the newest trends in home improvement.

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