Why Is There Gas In My Oil Lawn Mower?

Shocked as to why your oil is smelling like gasoline? It’s probably because gas leaked into the engine and mixed with the oil. But don’t freak out, it’s a pretty common problem.

So, you might ask yourself “why is there gas in my oil lawn mower?”

A faulty carburetor float or needle valve may be to blame. A faulty mechanical fuel pump could also be a reason. In both cases, you have to fix and examine the carburetor. All of these steps start by turning the fuel line off. Fixing these issues should stop the gasoline from leaking into your engine.

It’s natural to feel a bit lost from this amount of information. Unless you’re a mechanic this won’t help you. But don’t worry, we won’t leave you out to dry. 

Keep reading to know the details!

How to Know If There’s Gas in the Lawn Mower for Real?

One of the sure-fire ways of testing for gas in your oil is through smell. A strong gas odor coming from your oil is an indicator of a leak. You can easily detect this smell when you’re changing your oil.

Another symptom is when your pressure gauge is low. When your oil pressure indicator reads low, it usually signifies too much fuel has spilled in. 

If your oil levels are rising without adding oil, then gas has mixed in. One of the rarest problems is when your engine seizes up. Your engine stops working if there’s a fault in the combustion chamber.

Reasons Behind the Leak

Now, let’s look at the two common culprits behind the issue. Both of these are vital elements in the combustion process. Let’s go over these reasons in detail.

1. Dysfunctional Carburetor Float Or Needle Valve

The carburetor is responsible for injecting fuel into your pistons. On the inside of your carburetor bowl lies the float. Whether the float rises or drops depends on the gas amount in the bowl. 

The needle valve controls the amount of gas that goes into the float bowl. It also does this by moving up and down to control the flow of gasoline.

When dirt or impurities builds up, the needle valve can’t move. This causes the gas to continuously fill up the bowl. Thus seeping into the engine when it’s in excess.

The Gasoline then seeps down to the ring around the pistons. The fuel eats away the ring causing the gasoline to mix with the oil.

Problem Diagnosis and Troubleshooting

You have to take apart the carburetor to diagnose this problem. To do this you’ll need a few things.

Here’s a list of the things you need-

• Adjustable Wrench
• Alligator Vice Grips
• Screwdrivers
• Carburetor Cleaners
• Wire Brush

Now that we’ve covered the tools, let’s get to it.

First, squeeze the fuel line with your vice grips to turn off the gas to the carburetor.

If you’re having a hard time choosing a vice-grip, pick from our selection-

Next, take off the carburetor bowl retainer. It looks like a bolt head with an adjustable valve through it. Use a wrench to remove it.

If you’re unsure about which wrench to invest in, take a look at our picks below-

Then, remove the bowl with care, using gradual, gentle side-to-side motions to avoid damaging the sealing o-ring. Clean the carburetor with the cleaning solvent and wipe the debris off. 

Use a wire brush to do this. If you’re unsure about which one to pick, choose from our table below-

When the bowl is removed, you’ll notice a retaining pin dangling from the float. Remember to hold the float as you take off the retaining pin.

Finish off by examining the needle valve that connects to the float. Replace the needle valve or seat, if there are signs of wear and tear.

2. Faulty Mechanical Fuel Pumps

Faulty mechanical fuel pumps are the second most prevalent reason. This may or may not be relevant to you. Ignore this if your fuel pump’s not located on the side of your engine.

Problem Diagnosis and Troubleshooting

Follow these instructions if you have a fuel pump and no carburetor problems-

The tools needed for this will be the same as in the previous section. So let’s get to it.

As previously stated, turn off the fuel. Both the inlet and exit fuel lines must be removed. Make sure to remove them using the vice grips.

Next, take the pump off from the engine. You can do this by removing the two retaining nuts. Then, connect the gasoline lines to the removed fuel pump and restart the engine.

Remember to examine the pump for gas leaks by manually moving the pumping lever. If you’ve followed our instructions it should run without a hassle.

If not, take it to an actual mechanic as the pistons may be damaged.

To summarize, this is why your engine oil has gasoline mixed in it. Ensuring proper cleaning and reinstallation should take care of the problem.

Frequently Asked Questions

Question: Is my synthetic oil supposed to smell like gasoline?

Answer: It’s completely natural for synthetic oil to smell like gas or gasoline.

Question: Will loose spark plugs cause a bad smell?

Answer: Yes, it will. Your engine’s spark plugs must be tightened, or else gasses will seep into the combustion chamber. This component is located directly adjacent to your HVAC intake, you may sense a gasoline odor.

Question: Is Gasoline supposed to evaporate from my oil?

Answer:  Yes, gasoline vaporizes on its own. Since it’s a mixture of compounds, that contributes to the rate of evaporation. In addition, the compounds used in the refining process make gasoline volatile.

Bottom Line

Now you have the answer to your question of why is there gas in my oil lawn mower?. If you’ve followed our instructions properly, there shouldn’t be any more problems now.

Let us know about your experience with this. Stay safe and say goodbye to your tainted oil now!