Can Old Gas Cause A Lawn Mower Not To Start

One common issue with lawn mowers is difficulty starting, and this may be due to old gasoline. In our post on Can Old Gas Cause a Lawn Mower Not to Start?, we provide expert advice on how to diagnose and solve this problem.

For other potential hazards to your lawn mower, check out our post on Can Wet Grass Break a Lawn Mower? Landscape Advice for tips on mowing safely in wet conditions.

And if you’re interested in unconventional methods of lawn care, our post on Can Soap Help My Lawn? Expert Recommendations explores the use of soap in your lawn care routine.

Old gas can cause a lawn mower not to start by clogging the carburetor and preventing the engine from getting enough fuel.
To prevent problems with old gas, try to use fresh gas whenever possible and consider using a fuel stabilizer if you plan to store your mower for an extended period.
Troubleshooting a lawn mower that won’t start involves checking components like the battery, air filter, spark plug, and gas level.
Changing the oil in your lawn mower at least once per year or every 50 hours of use will help keep your machine running smoothly.
In addition to regular maintenance, using soap and aerating your lawn can promote a healthy lawn that is less susceptible to problems like weeds and pests.

Explore our comprehensive resources on lawn care and maintenance to keep your equipment in top condition and your lawn healthy and vibrant.

Can Old Gas Cause A Lawn Mower Not To Start

There are several reasons why old gas won’t work in your lawn mower. One of them is that gasoline has an indefinite shelf life and will continue to be good for years after it’s been bought and sold by the retailer. 

The other main reason is that as time goes on, ethanol-based fuel becomes more acidic and less combustible, which causes problems with the engine of any equipment that uses it.

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Can Old Gas Cause A Lawn Mower Not To Start?

You’ve heard this before: use fresh gas in your lawn mower to get the best results. But what does “fresh” mean? What’s a safe amount of time between fills?

 How long can you keep old fuel in your lawnmower’s tank before it stops working well or not at all? It’s hard to know!

What makes it so difficult is that there are several ways old gas can cause problems for your lawn mower, and many factors (like how cold the weather is) that determine whether those problems will show up. 

It all depends on how you store your fuel, how much ethanol is in it, and even which brand of gasoline you buy! So let’s talk about some specific situations where using old fuel could cause trouble for your machine.

When was the last time you filled up? If it was more than three months ago, then most likely any damage from using bad gas has already happened by now. 

Don’t worry about checking for corrosion or anything like that just yet just make sure that everything else looks okay under there first. 

If everything looks good then go ahead and start taking apart some parts until they’re clean enought to see clearly through them again.

Top Reasons Lawn Mower Not Starting

What’s The Best Fuel For A Lawn Mower?

Ethanol-free gasoline is the best fuel for your lawn mower. This type of gas will provide you with the best performance and longevity from your machine. 

Otherwise, you may experience problems like engine damage or poor performance because ethanol can eat away at the metal in engines.

Ethanol-free gasoline is also the only kind that’s safe to use in a carbureted engine after it has been damaged by ethanol-based fuel. 

If you do use straight alcohol, remember that it requires about twice as much energy to ignite as regular gas does which can make starting a cold engine difficult if there isn’t enough preheat time before attempting ignition.

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What Is Ethanol?

Ethanol is a fuel made from plant matter. It can be used as an alternative to gasoline, diesel, propane and other types of fossil fuels. 

Ethanol can be produced from corn, sugarcane or cellulose (a form of plant matter). In the United States, most ethanol comes from corn grown in large monoculture fields that require extensive fertilizers and pesticides to grow.

Ethanol has been around for centuries but got its start in modern times when the German chemist Nicholas Rudolph created it in 1846 by distilling wood chips with sulfuric acid and sodium hydroxide. In 1908 he was able to refine it further into an alcohol-based fuel which he called “ethyl alcohol.”

How Does Ethanol In Gas Affect Engines?

Ethanol has a lower octane rating than gasoline, which means that it can knock more easily when mixed with air. 

This means that the fuel is less stable when mixed with air, which can lead to engine damage. The higher octane ratings of ethanol-free gas will help prevent your engine from knocking or pinging when you use old gas containing ethanol.

Why Is Ethanol Bad For Cars?

The reason ethanol is bad for cars and lawnmowers is because it causes corrosion to the fuel lines and carburetor, as well as other parts of the engine. 

If you have an older model car, it’s possible that using ethanol-containing gas may cause damage that isn’t covered by your auto warranty (not to mention the cost of repairs).

In some cases, replacing the carburetor can fix this issue. In others, you’ll have to replace other parts of your engine or even buy a new one altogether!

Why Is Ethanol Bad For Lawn Mowers?

The most common way to damage an engine with ethanol-blended fuel is through corrosion. Ethanol attracts water, which helps it evaporate quicker and gives it a higher octane rating than gasoline, but this can cause your car’s tank or lines to rust up faster. 

If you keep using the same container of old gas for the whole season and don’t change your oil regularly, you’ll be sure to notice some problems with your lawn mower’s performance.

Another problem with ethanol-based gas is that it can cause carburetor damage if left in an engine too long after being used up especially if there isn’t much air flow keeping oxygen moving over valves and spark plugs during operation. 

The increased moisture content in this type of fuel also causes many engines’ fuel injectors (which send fuel into cylinders) to clog up when trying to deliver enough power at higher speeds (like those found when cutting grass). 

Finally, although there aren’t many reports about problems caused by ethanol-containing fuels like E10 or E15 causing filters inside cars’ engines not working well either before or since being filled up at stations selling these kinds of products; because these substances contain more contaminants than traditional gasoline does (which will get trapped inside filter elements).

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How Do I Know If My Engine Has Been Damaged By Ethanol?

You may notice that your engine runs better after you’ve been driving it for a while. That’s because when the ethanol evaporates, some of the water that was dissolved in it remains behind in the gas tank and intake manifold. 

So when you start up again after sitting for a while, you’ll have more lubricating oil mixed with your fuel than before. This is good news if you have a carbureted engine but not so great if yours has fuel injection (unless of course your car has been running on E85 which is 85% ethanol).

How Can I Fix The Damage From Ethanol?

Clean the carburetor. This is the first thing you should do when your lawnmower won’t start, because a clogged fuel filter can be caused by old gas. A dirty carburetor may cause your lawnmower to run poorly, so make sure it’s clean before trying anything else!

Replace the spark plugs. If your engine isn’t firing properly, replacing some spark plugs could help get it running again. Just make sure that you’re using ones that match what came with your engine otherwise they might not fit correctly or fire at all!

Reinstall the air filter and check its condition regularly afterward to keep everything running smoothly!

Is It Safe To Use Ethanol-Free Gas In An Engine That Has Been Damaged By Ethanol?

Yes, it is safe to use ethanol-free gas in an engine that has been damaged by ethanol. The ethanol-free gas will not cause further damage to the engine because they are two different types of fuel; one cannot harm another. You can use ethanol-free gas for the rest of the season without worry of causing further damage to your lawn mower’s engine.

Can I Use Straight Alcohol As Fuel For My Lawnmower?

The answer to this question is “yes,” you can use straight alcohol as fuel for your lawn mower. However, there are some caveats to consider before you do so.

First, not all lawn mowers are designed to run on pure alcohol fuel (PAF). If your model was manufactured after the mid-1980s and runs on gasoline with 10 percent ethanol already added, it should be fine with PAF; however older models may be damaged by PAF and require repair or replacement parts. 

Second, while PAFs are inexpensive and easy to find at any hardware store or gas station that sells fuel additives (most large chains carry them), they can sometimes be difficult to locate when you need them most during a Sunday afternoon session at an empty hardware store where all roads lead back home and the only thing available is coffee from Starbucks so plan accordingly! 

Finally (and this one’s pretty important), if your engine has been damaged by ethanol before running PAFs through it again could cause more serious problems such as damage beyond repair!

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Can I Mix Alcohol With Gasoline In My Lawnmower?

You can’t mix fuel additives with gasoline, so if you’re going to use alcohol-based fuel in your lawnmower, you’ll need to add some type of stabilizer first. Mixing alcohol and gas isn’t recommended because the two fuels don’t mix well; alcohol is a solvent, which means it dissolves or softens other materials. 

The addition of an accelerant like ether would help them stick together better but makes things even more complicated. 

You’d also have to go through some extra steps before starting up your lawnmower because ether evaporates quickly when exposed to air so adding it requires special equipment that most people don’t have access too (unless they’re running an auto shop).

In short: Don’t try this at home unless you’re willing to invest in specialized equipment—it’s not worth ruining your machine just because someone told on Facebook that they did it once! But if you still want proof that ethanol causes engine damage and how exactly this happens then read on below

Why Did My Engine Stop Running After Using Alcohol-Based Fuel?

It’s important to know that alcohol-based fuel can damage your engine, especially if it’s older or less than perfect. This can cause your engine to stop running as well. So, how do you fix the damage? Can you still use alcohol-based fuel in an engine that has been damaged by it?

Yes! There are several different ways of repairing any damage caused by ethanol (which is the main ingredient in the common variety of alcohol-based fuel). 

And yes, it is safe to use non-ethanol based fuels such as Premium Unleaded Gasoline and Diesel Fuel after your engine has been damaged by ethanol (or any other type of alcohol).

Will Old Gas Give You Bad Gas Mileage?

It’s true that the longer you wait to fill up your lawn mower, the more gas mileage you will lose. Your vehicle’s fuel economy is a function of its engine efficiency and driving conditions (such as how fast you drive). 

For example, if you’ve been driving at 70 miles per hour on flat land for three hours straight with no stops, then it’s likely that your car will have consumed more than double what it would have at 50 miles per hour while going up and down hills.

Does Old Gas Cause A Lawn Mower To Run Poorly?

If you’re using old gas in your lawn mower, it can cause problems with your engine. The main problem is that ethanol attracts water over time and this can damage the engine. However, gasoline doesn’t go bad it’s the ethanol component that does that.

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Why Is It So Hard To Start A Lawn Mower With Old Gas?

If you’re wondering why it’s so hard to start a lawn mower with old gas, there are a few reasons. The ethanol in the old gas can clog the carburetor and the fuel injectors, which makes it difficult for your lawn mower to get enough fuel into its engine. 

The ethanol can also corrode the fuel lines and damage other parts of your engine if it’s been sitting around for too long. Plus, ethanol is bad news if you fill up with an unfamiliar brand of gasoline (and most people don’t remember what brand they used last time).

What Happens If You Fill Your Lawn Mower With Old Gas?

If you think that filling your lawn mower with old gas is going to save you money and make it easier on yourself, think again. You will have to replace the carburetor, the fuel filter, and possibly even more parts of the engine.

Think about what happens when you mix oil and water together: they separate apart because they don’t like each other. The same thing happens when ethanol mixes with regular gasoline: they separate apart in your car’s engine because they don’t like each other either!

Can You Keep Using The Same Container Of Old Gas For The Entire Season?

It depends. If you’re using the same container of old gas for the entire season, then it’s probably best to switch to a new container. Old gas can cause your lawn mower to run poorly and could even damage its engine if you keep using it.


We hope that we’ve been able to answer some of the questions you may have about using old gas. We also want to make sure that you know how important it is to keep an eye on your engine so that you can stop any damage before it happens. If you have any additional questions or comments, please let us know in the comments below!

Further Reading

Here are some additional resources related to lawn mower maintenance and troubleshooting:

Top 5 Mower Troubleshooting Tips from Briggs & Stratton – Learn about common lawn mower problems and how to troubleshoot them with this helpful guide from Briggs & Stratton.

Can Old Gas Cause a Lawn Mower Not to Start? – This article from Home Guides provides an in-depth explanation of how old gas can affect your lawn mower’s ability to start and what steps you can take to prevent this problem.

Starting a Lawn Mower with Old Gas – Lawn Chick offers some helpful tips and tricks for starting a lawn mower with old gas, including using fuel stabilizer and cleaning the carburetor.


What causes a lawn mower not to start?

There are several reasons why a lawn mower may not start, including a dead battery, clogged air filter, dirty spark plug, and old or bad gas.

How do you troubleshoot a lawn mower that won’t start?

To troubleshoot a lawn mower that won’t start, you should check the battery, air filter, spark plug, and gas level. You may also need to clean or replace some of these components if they are damaged or dirty.

Can old gas cause a lawn mower not to start?

Yes, old gas can affect your lawn mower’s ability to start by clogging the carburetor and preventing the engine from getting enough fuel.

How often should you change the oil in your lawn mower?

You should change the oil in your lawn mower at least once per year or every 50 hours of use, whichever comes first.

What is the purpose of a spark plug in a lawn mower?

The spark plug in a lawn mower provides the spark that ignites the fuel in the engine, allowing it to start and run smoothly.