Do You Mix Oil and Gas for Lawnmower? (What You Need to Know). Fuel for lawn mowers

Do You Mix Oil and Gas for Lawnmower? (What You Need to Know)

If you’re a new lawnmower owner, you might be wondering, “Do you mix oil and gas for a lawnmower?” And if so, what’s the oil and gas ratio you should add?

The short answer is that 2-cycle engine lawnmowers require a gas and oil mixture for fuel, while 4-cycle engines run on straight gasoline. The most common gas and oil mix ratio for lawnmowers are 50:1, but you’ll want to refer to your owner’s manual for your particular model’s recommended gas and oil mixture ratio.

This can be confusing, primarily if you’ve never owned a lawnmower.

In the following paragraphs, we’ve provided all the information you need to help you answer any questions you may have regarding this topic, so stick around.

Do You Mix Oil and Gas for Lawn Mower?

You might be able to mix oil and gas and add them to a lawnmower. However, it’ll all depend on the type of engine your mower has.

Some engines allow you to add oil and gas together, while others will only work if you add them separately. This is why it’s essential to know the type of engine your unit is housing before you start mixing oil and gas.

What Engines Can You Mix Gas and Oil In?

Lawnmowers typically house one of two types of engines. The first is the two-cycle/cylinder engine, and the second is a four-cycle/cylinder engine.

If you own a two-cycle engine, you can add a mix of gas and oil. But, per contra, if you own a four-cycle engine, you need to refrain from mixing the gas and oil, or it may damage your engine.

If you checked and saw that you own a four-cycle engine, you’ll also notice that there are different tanks and openings where you can add oil and gas separately.

How to Know If You Own a Two-Cycle or Four-Cycle Engine?

There are many ways you could differentiate between a two-cycle engine and a four-cycle one. The most common way is to check the engine’s port. If it only has a single opening, then it’s a two-cycle engine, and you can add your oil and gas mix without any worries.

If you find two ports separating two tanks, then it’s a four-cycle engine, and you’ll need to add your gas and oil separately.

Another way to recognize the engine’s type is by checking if there are any warning stickers against mixing oils and fuel. You might also find them already labeling the engine as either two-cycle or four-cycle—they can also be called two-stroke or four-stroke, respectively.

If you have any trouble finding out the type directly from the engine, you can check the user’s manual that came with the mower. The manufacturer will always mention whether it’s a two or four-cycle engine in the manual.

Guide For Mixing 2 Stroke Fuel For Garden Power Tool

What Is the Correct Oil-Gas Ratio to Add to Your Lawn Mower?

If you checked your engine type and found it to be a two-cycle, you can now add in your gas and oil mix. But before you do, you need to make sure you’re adding the appropriate amount.

The amount of gas and oil mixture you add will depend on how much your engine requires. Some two-cycle engines use a 50:1 gas to oil ratio; others use 40:1. Some older models may use 32:1.

You can check the ratio your engine uses by checking the port. Most engines will have the ratio written on the cover. If it’s not there, you’ll find it written in the user’s manual.

If you found that your engine uses a 50:1 ratio, you’ll need to mix around 2.6 ounces of oil with 1 gallon of gas.

If your engine uses a 40:1 ratio, add 3.2 ounces of oil to 1 gallon of gas. The 32:1 ratio will need 4 ounces of oil added to 1 gallon of gas.

What Type of Oil and Gas Should You Use?

Most manufacturers will include what type of oil and gas you should use on your grass cutter in their manuals. So checking the manual is a must.

If you have any trouble with the user’s manual, you can refer to the recommended type for each engine.

It’s advised for both two-cycle and four-cycle engines to use an unleaded gas with a minimum 87 octane rating and a maximum of 10% ethanol.

Most gas stations sell fuel with more than 15% ethanol, so be sure to check the ethanol percentage when buying your gas. It shouldn’t exceed 10%, or it may damage your engine.

As for the oil, there are oils available specifically for two and four-cycle engines, respectively, so it’s best to use them for your lawnmower depending on the type of engine you have.

How to Mix Your Gas and Oil Before Use?

Now that you have the gas and oil you need, you can start preparing your mix to use on your mower. Refer to the previous section to know the correct gas to oil ratio you should use.

The first thing you’ll need to do now is to prepare an empty gas bottle. Then, make sure it’s completely clean before adding the new gas.

Afterward, you can add in your oil and then start mixing. You can mix it up by stirring or shaking the bottle well. That should get your mixture ready for use.

Please note that you’ll need to use this gas-oil mixture for one month, or it’ll start losing its effect.

What Happens If You Add the Oil and Gas Mix to a Four-Cycle Engine?

All the previously mentioned steps are specifically for two-cycle engine use. Now, what if you accidentally added this newly made mix into a four-cycle engine instead?

As long as you notice the mistake quickly, there shouldn’t be much of a problem. You’ll need to drain all the mixture you just added out and replace it with the correct gas or oil per tank.

If you turn on your mower before you drain the mixture, it may, unfortunately, be too late, and you’ll start noticing your lawnmower smoking up.

Using an oil and gas mix on a four-cycle engine will cause it to overheat and eventually break down. So it’s best to be entirely sure of which type of engine your lawnmower has before use to avoid causing any damage.

How Often Should You Change Your Gas and Oil?

It’s recommended to replace your gas and oil mix after three weeks to one month of use. You can wait until two months to replace it, but it won’t be as effective anymore.

That’s why it’s better to use a new mixture every three weeks to get the best results and make sure you don’t exhaust your engine.


Lawnmowers tend to have two types of engines, and depending on which type they have, they can use a gas and oil mix, or you’ll need to separate the oil and gas from each other.

If you have a two-stroke engine, you can mix gas and oil without any problems. However, if your mower is equipped with a four-stroke engine, you can’t mix gas and oil. That’s why you need to know the difference before using it.


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I love working in the yard and coming up with projects around the house. In addition, I am blogger. I’ve decided to start this blog to share stuff I learn about yard work, or any projects that are house related. These days I blog about everything related to anything pertaining to the outside of the home. Everything in this blog should be used for educational purposes only. is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Privacy Policy

The Importance of Not Using Ethanol Gas in Lawn Mowers, Leaf Blowers, and Other Outdoor Power Equipment

As you drive around town, there’s a good chance you’ll see gas pumps with labels of “E10” or “E15.” This indicates that gasoline contains ethanol, a type of alcohol commonly made from corn. And even though electric vehicles are becoming more popular, most cars still run on ethanol-blended gasoline. But what about your lawnmowers, leaf blowers, and chainsaws? Is ethanol-free fuel the best choice for power equipment?

What is ethanol gas?

First, you may be wondering what ethanol gas is. Ethanol-blended gasoline is commonly sold at gas stations and used by most drivers. It typically contains between 10% and 15% ethanol, meaning it has been mixed with regular gasoline at a ratio of 9 parts gasoline to 1 part ethanol. E10 (10% ethanol) and E15 (10.5-15% ethanol) are both widely available and often cheaper than premium, non-ethanol fuels. While drivers choose ethanol gas over premium non-ethanol fuel to save money, non-ethanol fuel is better for your power equipment.

Here’s why non-ethanol fuel is the best option for power equipment

Non-ethanol fuel has better performance in more delicate machinery because it doesn’t contain additives that can corrode small parts over time. In addition, non-ethanol fuel does not absorb water, so it has a longer shelf life if properly stored—this makes it ideal for seasonal use, like snow blowers or leaf blowers.

According to Husqvarna, “E10 gas absorbs up to 50 times more water than standard gasoline.” One of the biggest reasons to avoid using ethanol gas in power equipment is that ethanol can dissolve plastic, rubber, and fiberglass, and even damage the interior components of power tools if used regularly.

Options outside of ethanol gas

The U.S. Department of Energy mentions a few different alternatives: compressed natural gas, biodiesel, and electricity.

Natural gas engines have an advantage over gasoline and diesel engines in that there are fewer harmful emissions. Additionally, natural gas can lower maintenance requirements.

Biodiesel, produced from something like vegetable oil, is “nontoxic and can reduce pollutant emissions compared with petroleum diesel.”

Electric mowers do not require as much maintenance. There are also corded electric leaf blowers.

Do not use ethanol gas in your power equipment

To sum up, most cars, trucks, and SUVs run on blended fuels containing 10% to 15% ethanol. However, when it comes to lawnmowers, leaf blowers, and chainsaws, opting for no-ethanol or ethanol-free gasoline is always going to be the better option.

Gas For A Lawn Mower – What You Should Know

Gas for a lawnmower is a tricky subject. It seems like everyone has an opinion on what type of gas to use and how much to put in the mower. The truth is that many different factors go into choosing which fuel will work best for your lawnmower. In this guide, we’ll discuss some of those factors so you can make an informed decision when it comes time to fill up the tank!

The type of gas you use depends on the engine in your lawnmower. Most lawnmower brands specify the best kind of fuel in the owner’s manual. If it’s a four-stroke engine, you can use unleaded gasoline with an octane rating of 87 but NOT higher. Some engines are also acceptable to use gas with 10% ethanol and don’t forget to use a fuel stabilizer.

Best gas for lawn mower

What kind of gas is best for lawn mower engines?

Many people wonder what kind of gas is best to use. There are a few different types, but two that seem most popular for lawn mowers are ethanol-free gasoline and premium octane fuel. The type you choose depends on the engine design of your specific model and how much power it produces when running at peak efficiency. Keep in mind that not every type will work with all engines, so if you have questions about whether or not one of these fuels would suit your needs, then be sure to check instructions for your engine!

Premium octane has been shown to burn more smoothly than other options and produce fewer emissions, which means many manufacturers recommend this option for those who want their equipment’s lifespan extended while also experiencing a quieter, smoother ride.

Ethanol-free gasoline is often the best option for equipment with smaller engines and those who are looking to save on fuel costs in general, but it’s not ideal if you’re worried about long-term wear and tear or want to maximize power at all times!

The type of gas used can make an impact on how much maintenance your lawnmower needs too. Premium octane has been shown to reduce engine knocking when gas gets too low, while ethanol-free gasoline may lead to more frequent clogs and other problems down the line. Consider these factors before deciding which fuel will work best for your specific needs!

Once you know the type of engine in your lawnmower, you can quickly determine the type of gas necessary to keep your machine working.

Four-Stroke Engines

The most popular type of engine for lawn mowers is a four-stroke. It’s also the safest and most reliable option as it requires far less maintenance than other types, making it perfect if you’re looking to avoid any unnecessary problems in the future!

A four-stroke engine can be identified by two valves that open at different times during an operation cycle; one opens on the downward stroke while the second valve stays closed until after combustion has occurred. This means there are two power strokes per revolution instead of just one like with a three-cycle engine.

When considering which fuel would work best for your specific needs, many things come into play: You have to make sure you use gas without ethanol (if possible) and with a high octane rating (usually 91 or higher). This type of fuel has been shown to reduce engine knocking, which means you’ll need less maintenance over time.

If your goal is to maximize power at all times, then be sure that the gas you use contains premium additives to increase the energy released during combustion.

The best option for those who want their equipment’s lifespan extended while also experiencing quieter operation would be ethanol-free gasoline, as it burns more smoothly than other types! Be aware that these fuels may cost more, but they’re worth it if long-term wear and tear is something you care about.

Two-Stroke Engines

The other type of engine found on a lawnmower is the two-stroke. This design has been around since the late 1800s and offers some different benefits over its popular counterpart. Still, it requires more frequent maintenance than others to keep operating reliably.

A two-cycle gasoline engine’s piston will turn twice for every crank revolution instead of once like with a four-stroke engine; this means that there is just one power stroke per crankshaft rotation, unlike with a four-stroke model where there are two.

Some people might be wary about using ethanol fuels as they have fewer octane levels than premium gas or regular fuel, so you’re likely going to need to make sure your equipment isn’t exposed to extreme temperatures if you want to avoid experiencing engine knock.

Two-stroke engines are more responsive than four-strokes, but they do require a bit more gas simultaneously, which may make them less economical in the long run versus other types of equipment!

You also have an option when it comes down to oil for your engine; depending on what type is used will depend on how often you need to change it and whether or not maintenance checks should be done annually instead of semi-annually (which is usually recommended). Be sure that whatever type is selected has been tested for use with two-stroke gasoline mowers before applying anything!

These instructions can save you from any unnecessary breakdowns, so be sure to follow all guidelines carefully when refueling your machine.

Do I need a Fuel Stabilizer for a lawnmower?

For those who have a gas-powered lawnmower, one of the most important questions you may face is how to store gasoline for use properly. A fuel stabilizer will keep your gas fresh and avoid any problems that might arise when using it next season if stored in an appropriate container or tank.

If you decide not to add a stabilizer, make sure your mower has been fully drained from all fluids before storing, as this can help prevent corrosion and other issues from arising over time.

You also need to consider whether or not the type of gas offered meets EPA standards so that you’re able to protect yourself against future fines! All fuels should contain no more than 15% ethanol by volume, but some fuels will have a higher ethanol content than those that are not, and you’ll need to look for information about this if you’re concerned.

If the gas pump doesn’t offer any labeling or has just an “E” on it, then be sure to ask before filling up your tank!

How much gas does a lawnmower use?

A lawnmower typically uses around one gallon of gasoline for each hour it runs. That’s 0.25 gallons per minute or roughly four to five minutes driving time, which is how fast most people motor about properties with a gas-powered machine in tow. For instance, if you use the mower on your yard for two hours every week, then you would be using eight gallons of gas per year—or 56 depending on the price!

Where to buy gas for a lawnmower?

Where gas for lawn mower is sold depends on where you live. In rural areas, it may be possible to find a gas station where one can fill up their tank with gasoline or other fuel; in more densely populated areas such as towns and cities, this will not always be the case. Alternatively, many independent shops specialize exclusively in selling fuels of all types. Here’s what we recommend:

  • Some major chains sell both oil-based (gasoline) products and ethanol blends like E85 from time to time but don’t guarantee they’ll have them all year round.
  • Gas stations also come in several different varieties and sizes–some customers prefer full-service pumps while others would rather self-serve.
  • Since gas stations are generally either self-service or full-service, it’s important to know what type you’re looking for when deciding where to buy gas. Full-serve fuels may be more expensive, but they offer additional benefits such as free air and water (some customers find useful). Fuel fluctuate a great deal from coast to coast and country to country, so if you need help figuring out how much your fuel will cost ahead of time, we recommend using GasBuddy.
  • Some areas offer specific types of gasoline that can sometimes lead people who ignore spending extra money on something their vehicle doesn’t actually require–for example, in the United States, most cars run just fine on regular unleaded gasoline even though there are alternative blends available.
  • For those who choose to buy gas in a canister or jerrycan, there’s more work required since the fuel must be poured into the mower tank and then transferred using an additional hose (which may not come with your purchase). The upside is that it will last for months as opposed to being used up pretty quickly.
  • Finally, if you know what kind of engine your lawn equipment has–whether it runs on gasoline or ethanol-blended fuels like E85–you’ll have a better idea about where you should go when looking for gas.
  • A quick word about prices: Gasoline costs vary from place to place, so while one town might offer regular unleaded at 0.97 a gallon, the next town over might have it priced at 0.91 a gallon.
  • In addition to that difference in pricing, gas is also sold by volume, so you’ll see listed per liter or quart.
  • Gasoline with ethanol can be cheaper than gasoline without ethanol if your car’s engine is compatible–read more about compatibility below!
  • If one lives somewhere where there are plenty of stations nearby, and competition between them keeps low, they will likely find their best deal on fuel for lawn mower buying from the “lowest price” station (instead of paying whatever cost happens to be posted).

Learn How to Gas Up Your Lawn Mower

You’ll need to know the type of lawnmower by the engine. Your owner’s manual should provide you with the exact type of engine and even the best fuel.

There are typically two types of lawnmower engines: four-stroke and two-stroke engines. However, most lawn mowers today have four-stroke engines. Larger engines will have 140-cc to 190-cc. These are made for taller, more robust grass and leaf mulching (for instance, you can find the best lawnmowers for 1 acre here).

How to fill a lawnmower with gas

When purchasing a lawnmower, you should always check that the gas tank and oil chamber are easy to find, as you’ll be maintaining these fuels throughout the lifetime of your mower.

Step 1: Locate the Gas Tank

Most walk-behind lawnmowers have a small plastic tank on the side of the mower or at the back. It’s typically located on one side towards the back in riding mowers, just like a car.

Other mowers have a covered gas tank that’s hidden. You may have to find it underneath a cap or symbol.

Step 2: Remove Gas Cap

Just like a car, you’ll typically need to remove a cap by twisting it counterclockwise. There may also be caps that lock in place or others that require a key.

Step 3: Fill Up Your Tank

Determine what gas is best for your engine. If it’s fresh, unleashed gasoline, you can get the same fuel at a gas station.

It’s best to use a nozzle or funnel to spill gas as you pour. Take your time as you pour and pay attention to the fill line in your gas tank.

Step 4: Tighten the Gas Cap and Go!

After you fill the tank, make sure to put the gas cap back on and tighten it. Your mower should be ready to go.

Mistakes to Avoid When Filling Up Lawn Mower

Lawnmowers can be finicky machines. This is because they are typically left in storage for many months when it gets colder or used too frequently to cut moist grass. If not cleaned properly, your lawnmower may stop firing up at all.

  • Draining the tank harms your lawn mower’s carburetor
  • Small droplets of gas are left behind and typically start to get sticky, like a varnish
  • If gas gets stuck in the needle valve tip, the carburetor will be damaged and won’t work properly
  • Gas tanks shouldn’t sit empty for long periods as water vapor can get in the tank and start to condense, triggering rust and corrosion
  • Use a gas stabilizer agent instead when storing your lawnmower

To use a gas stabilizer, you’ll fill your tank almost entirely with fresh, clean unleaded gasoline. Then add a fuel stabilizer. You can use this with old fuel, but it’s best to use it when fresh.

Turn on your lawnmower and let the engine run for a few minutes to get the stabilizer running through your fuel lines and carburetor. Your lawn mower should be ready for storage now.

Do You Put Same Gas as Cars in Lawn Mowers?

Most lawnmowers work with the same gas you put in your car, but be sure to search for your lawnmower model and see what other people recommend online!

Older models of lawnmowers often don’t handle ethanol well.

Today’s gasoline contains up to 10% ethanol, so always check first before filling up at a gas station near you.

To make it easier on our lawnmower, we use automotive 87-octane gasoline with a fuel stabilizer.

Do You Add Oil Separately in Lawn Mower?

When it comes to maintaining your lawnmower, you’ll need to check and replace the oil from time to time.

You should change the oil for all new mowers after the first five hours of use; then, you’ll change it before a new mowing season in spring or summer. This also equates to about 50 hours of use.

Most lawn mowers have a separate oil chamber with an oil plug. You’ll need to check the oil filter to see if it’s filled with oil debris. If so, this should be replaced as well.

Lawn Mower Filters

Did you know that your lawnmower may also have oil and air filters? Depending on your model, you may have multiple filters that need to be checked periodically.

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It’s best to replace an oil filter once a year or before heavy-duty lawn mowing in early spring and summer.

lawnmower, need, know, fuel, lawn

Doyle Mathews Lawn Expert

Pro Tip: Mower air filters should also be replaced every three months if consistently mowing each week. For many, you are replacing your air filter once per year before summer is enough. There are also two filter types for specific mower models, including the primary filter and a foam filter.

Most mowers have paper air filters that prevent any large particles from getting into the combustion chamber. You can find these filters located beneath the cover of your lawnmower, but it’s best to check your manual specifications.

TruFuel 4-Cycle Ethanol-Free Fuel – Best fuel for lawnmowers

TruFuel is the world’s cleanest fuel. With a pre-blended mix, TruFuel starts quickly and runs at peak performance. TruFilters keep you running smoothly with no smoke—meaning it’s easy to tell when it’s time to get new filters. Rest assured that this fuel will not void your warranty or reduce equipment life due to fouling from high aromatic content fuels. Made for outdoor power equipment, TruFuel delivers superior performance in all four-cycle engines and helps extend the life of your machinery. You’ll even enjoy easier start-up, increased trigger response, smoother idling, cleaner-burning without smoke!

VP Small Engine Fuels 6208 Ethanol-Free 4-Cycle Fuel

VP Small Engine Fuels are engineered to maintain your fuel system not only for the day but for years ahead. With our new VP Fuel Ethanol Free 4-Cycle Fuel, you won’t have to worry about it attracting moisture or oxidizing and forming gummy deposits in your carburetor. Plus, with a flashpoint of.22 degrees Fahrenheit, this fuel burns cleaner, maintaining maximum performance without jeopardizing engine life!

  • No Ethanol, No Additives.
  • Great for sensitive engines like hand-held lawnmowers and blowers
  • Non-Premium but with all the benefits of Premium Fuel
  • Great for California because there’s no risk of Blended E10 Fuels
  • Leak issues during shipping

STIHL 7010 871 0203 Motomix 50:1 2 Cycle PreMix Fuel

STIHL is the name to trust when it comes to dependable garden implements, and now you can trust them with your prized 2-Cycle engine. Get the best of both worlds with a convenient 50:1 premixed fuel that makes life so much easier! Trust STIHL for everything from auto repairs, home appliances, power tools, lawn equipment, and tractor attachments – as well as this handy little pre-mixed fuel. It’s a no-brainer when it comes to small engine mixers. Make a good investment in your favorite gear by going with nothing but the finest quality like STIHL Premix Fuel Motomix 50:1 available right here.

  • No more mixing gas and oil, just open the can
  • Easy to pour and use for backup fuel
  • Works perfectly with any 2-cycle small engine
  • Reduces downtime because of keeping a peace of mind
  • Overpriced

TruFuel 2-Cycle 40:1 Pre-Blended Fuel

TruFuel is your pre-blended fuel for portable gas-powered equipment; it has been specifically designed to work best with 2-cycle engines and provides consistent performance. Whether you’re using air dampers or throttles to control oil and fuel delivery, TruFuel ensures that there will be no smoke from your engine. With higher quality synthetic oils in the mix that protect against heat build-up and virtually zero aromatics, which lead to better burning, you can be sure you’re getting an excellent product here. The convenient aspect, in particular, is a big highlight – TruFuel saves time by delivering everything perfect for usage without any messy mixing yourself! And those handy benefits all go hand in hand with reducing chemical emissions into our environment!

  • Long-term engine health
  • Ethanol-free fuel that meets international standards
  • 100% synthetic oil that exceeds test requirements for ISO L EGD and API TC
  • Stabilizer to help prevent deposits on the valve seat, cylinderhead and pistons
  • Too expensive for pro lawn service use

Goplus 20 Liter (5 Gallon) Jerry Fuel Can with Flexible Spout

Some might call it a “filler” fuel can, but we prefer to call it peace of mind. This 20 liter (5 gallons) Jerry fuel can from Goplus is perfect for transporting, storing, and dispensing oil- or gas-, based liquids in various environments with its tough steel construction and anti-corrosive coated paint inside and outside that eliminates the risks of rusting! Each can comes with a safety spout that locks onto the tank conveniently on one side to prevent spills–perfect when refueling your vehicle at an off-road destination!

The size and weight of these cans are compact and convenient for easy storage and transport. One Jerrycancano provides you with enough gas for 1 hour of mowing on a lawn – they can act as an emergency fuel supply in your car or home if the unfortunate should happen!

  • 5 gallons
  • Locking Lid Anti-Leak Protection
  • EPA and CARB Approved
  • Prevent leakage with the spill-proof seal, provide a more secure guarantee
  • Lightweight with compact size, easy to carry to any places you want
  • Top-grade material and fine workmanship ensure its good durability and reliability
  • Empty the can in seconds with the unique air breather
  • Spot welded handles indicate that the manufacturer is from China, not the US


How To Remove Gas From A Lawn Mower?

First of all, you need the fuel line disconnected (spark plug on lawnmower should be without fuel pipe). Secondly, take a liquid hand pump. one side should be in the gas tank, another in the gas can, and start pumping. That’s it!

What Fuel Do You Use?

Whatever the manual calls for. Because different manufacturers make their own standards for various engines.

How much gas does a zero-turn mower hold?

The capacity of a zero-turn mower varies by model, but most can hold anywhere from.75 to over one gallon. Many owners purchase two or three gas cans when they buy their mowers toy with enough fuel available for extended projects without refueling constantly.


Fuel is essential to maintaining a long lifespan for your lawnmower. When considering the type of gas that would be best for your mower, keep in mind what kind of engine it has and how much power it needs. Most riding mowers use the same type of gas as cars, but there are some differences when using high ethanol gasoline, so avoid this if possible. You should also monitor oil levels and change filters regularly to optimize performance. What other tips can you think of?

Lawnmower Won’t Start? Do this.

Bad gas or a dirty carburetor are the most common reasons for a lawnmower that starts hard or runs rough.

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A lawnmower that won’t start, especially when taken from storage, is almost always due to one problem: bad gas.

Storing a lawnmower in the fall without adding gasoline stabilizer to the fuel tank can cause the fuel to break down and plug the fuel passages. If fixing that problem doesn’t help, there are a few others that can help fix a lawnmower that won’t start, as we explain here.

How to Fix a Lawnmower That Won’t Start

Replace the Bad Gas

Over time (like the six months your lawnmower sat in your garage over the winter), the lighter hydrocarbons in gas can evaporate. This process creates gums and varnish that dirty the carburetor, plug fuel passages and prevent gas from flowing into the combustion chamber.

The carburetor bowl below formed corrosion and deposits during storage, which can easily plug fuel passages and prevent the engine from starting.

Storing equipment without stabilizing the gas can lead to deposits that foul the carburetor or injectors.

Ethanol-containing gas can absorb water from the atmosphere, which can lead to phase separation, which occurs when ethanol and gas separate, much like oil and water. Ethanol that has absorbed enough moisture and has sat long enough can foul the fuel system and prevent the engine from starting.

No matter how many times you yank the pull cord and pollute the air with your advanced vocabulary, the lawnmower won’t start if it’s trying to run on bad gas.

In extreme cases, evaporation of lighter hydrocarbons can change the gasoline’s composition enough to prevent it from igniting. The gas may be fueling the engine, but it doesn’t matter if it won’t ignite.

Bad Gas in Your Lawnmower? Here’s How to Fix It

If you neglected to add gasoline stabilizer to the fuel prior to storage, empty the tank and replace with fresh gas. If the tank is nearly empty, simply topping off with fresh gas is often enough to get it started.

On some mowers, you can easily remove and empty the fuel tank. Sometimes that’s more trouble than it’s worth. In these cases, use a fluid extraction pump or even a turkey baster to remove the bad gas. You don’t need to remove all of it; but try to get as much out as possible.

Clean the Carburetor

You’ve replaced the fuel, but your lawnmower still won’t start.

Next, try cleaning the carburetor. Remove the air filter and spray carburetor cleaner into the intake. Let it sit for several minutes to help loosen and dissolve varnish and gums.

Remove the air filter and spray carburetor cleaner into the intake. Let it sit a few minutes to loosen deposits.

On some carburetors, you can easily remove the float bowl. If equipped, first remove the small drain plug and drain the gas from the bowl. Remove the float bowl cover and spray the float and narrow fuel passages with carburetor cleaner.

This kind of “quick-and-dirty” carburetor cleaning is usually all it takes to get the gas flowing again and your lawnmower back to cutting grass.

If not, consider removing the carburetor from the engine, disassembling it and giving it a good cleaning. Be forewarned, however: taking apart a carburetor can lead to nothing but frustration for the uninitiated. Take pictures with your phone to aid in reassembly. Note the positions of any linkages or the settings of any mixture screws, if equipped. If you’re at all reluctant, visit the servicing dealer instead.

Consider replacing the carburetor altogether. It’s a fairly simple process on most smaller mowers and it’s often less expensive than taking it to the dealer.

Direct compressed air from the inside of the air filter out to remove debris that may be reducing airflow and preventing the lawnmower from starting.

Clean/Replace the Air Filter

With the air filter removed, now’s the perfect time to clean it.

Tap rigid filters on a workbench or the palm of your hand to dislodge grass clippings, leaves and other debris. Direct compressed air from the inside of the filter out to avoid lodging debris deeper into the media.

Use soap and water to wash foam filters. If it’s been a few years, simply replace the filter; they’re inexpensive and mark the only line of defense against wear-causing debris entering your engine and wearing the cylinder and piston rings.

An incorrectly gapped spark plug can prevent the engine from starting. Set the gap to the specification given in the owner’s manual.

Check the Spark Plug

A dirty or bad spark plug may also be to blame. Remove the plug and inspect condition. A spark plug in a properly running four-stroke engine should last for years and never appear oily or burned. If so, replace it.

Use a spark-plug tester to check for spark. If you don’t have one, clip the spark-plug boot onto the plug, hold the plug against the metal cylinder head and slowly pull the starter cord. You should see a strong, blue spark. It helps to test the plug in a darkened garage. Replace the plug if you don’t see a spark or it appears weak.

While you’re at it, check the spark-plug gap and set it to the factory specifications noted in the lawnmower owner’s manual.

If you know the plug is good, but you still don’t have spark, the coil likely has failed and requires replacement.

Did You Hit a Rock or Other Obstacle?

We’ve all killed a lawnmower engine after hitting a rock or big tree root.

If your lawnmower won’t start in this scenario, you probably sheared the flywheel key. It’s a tiny piece of metal that aligns the flywheel correctly to set the proper engine timing. Hitting an immovable obstacle can immediately stop the mower blade (and crankshaft) while the flywheel keeps spinning, shearing the key.

In this case, the engine timing is off and the mower won’t start until you pull the flywheel and replace the key. It’s an easy enough job IF you have a set of gear pullers lying around the garage. If not, rent a set from a parts store (or buy one…there’s never a bad reason to buy a new tool) or visit the dealer.

My Lawnmower Starts But Runs Poorly

If you finally get the lawnmower started, but it runs like a three-legged dog, try cleaning the carburetor with AMSOIL Power Foam. It’s a potent cleaning agent designed to remove performance-robbing carbon, varnish and other gunk from carburetors and engines.

Add Gasoline Stabilizer to Avoid Most of These Problems

Which sounds better? Completing all these steps each year when your lawnmower won’t start? Or pouring a little gasoline stabilizer into your fuel tank?

Simply using a good gasoline stabilizer can help avoid most of the problems with a lawnmower that won’t start.

AMSOIL Gasoline Stabilizer, for example, keeps fuel fresh up to 12 months. It helps prevent the lighter hydrocarbons from evaporating to reduce gum and varnish and keep the fuel flowing. It also contains corrosion inhibitors for additional protection.

I have a five-gallon gas can in my garage from which I fuel two lawnmowers, two chainsaws, two snowblowers, a string trimmer, an ATV and the occasional brush fire. I treat the fuel with Gasoline Stabilizer every time I fill it so I never have to worry about the gas going bad and causing problems.

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You can also use AMSOIL Quickshot. It’s designed primarily to clean carburetors and combustion chambers while addressing problems with ethanol. But it also provides short-term gasoline stabilization of up to six months.

Use a Good Motor Oil for Your Lawnmower

Although motor oil has no bearing on whether your lawnmower starts or not (unless you don’t use oil at all and seize the engine), it pays to use a high-quality motor oil in your lawnmower.

This is especially true for professionals or homeowners running expensive zero-turn or riding mowers.

Lawnmower engines are tougher on oil than most people realize. They’re usually air-cooled, which means they run hotter than liquid-cooled automotive engines.

Why Is There Such A HUGE Difference In Gas/Oil MIX RATIOS? (DAY 12)

They often run for hours in hot, dirty, wet conditions. Many don’t have an oil filter, further stressing the oil.

In these conditions, motor oils formulated for standard service can break down, leading to harmful deposits and reduced wear protection.

For maximum performance and life, use a motor oil in your lawnmower designed to deliver commercial-grade protection, like AMSOIL Synthetic Small-Engine Oil.

Its long-life formulation has repeatedly demonstrated its ability to safely exceed original equipment manufacturer (OEM) drain intervals in the toughest conditions. It provides an extra measure of protection when equipment goes longer between oil changes than is recommended by the OEM.

What Fuel Type to Use in Your Lawn Mower and Small Engines

Most homeowners own different small engine equipment to help them maintain their house. From blowing off leaves in the front yard, to cutting the grass in the backyard. Small engine maintenance involves knowing the best fuel type for the equipment you own.

Know the best fuel for your lawn mower and small engines

In buying fuel for the equipment, remember to read the manual completely and take note of the recommendations it says. However, here are some tips to help you find the best fuel for your equipment.

Lawn mower

Every homeowners uses a lawn mower to maintain their yards, both front and back. Using it regularly consumes a big amount of fuel, which results in refuelling it more often. Due to the urgency of the task, some homeowners pick a different fuel than the one recommended. This may cause a malfunction in the lawn mower.

Most lawn mowers found in hardware stores use four-stroke engines. This kind of engine needs fresh unleaded gasoline. Make sure to get gasoline with an octane rating of 87 or more. Owners may use gasoline with ethanol. However, gasoline with an ethanol content of 10% is not usually recommended.


People use chainsaws to cut trees and chop lumber. However, most fuels possess an octane rating of 87; chainsaws need more gasoline to work properly without any problems. The recommended gasoline for chainsaws needs an octane rating of at least 89 or more. Most classify chainsaws as high performance engines. A number of chainsaws produce more power than a lot of race car engines. This means that chainsaws work better with gasolines that possess higher octane ratings.

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Some chainsaws with two-stroke engines need an oil/gas mixture. Some two-stroke engines work best with these ratios:

Weedeaters, Brushcutters, String Trimmers

Homeowners use these tools to maintain the length of their grass. Keep it at minimum length to avoid getting pests or hinder the growth of the plants in the yard. These tools use unleaded gasoline that has an octane rating of at least 87. Avoid using gasoline that contains an octane rating lower than 87 or even diesel. Always use fresh gasoline for these.

Just like most chainsaws, these tools mostly use two-stroke engines that require an oil/gas mixture. Most of these equipments need a 40:1 gas-to-oil ratio, which means 2.6 fluid ounces of two cycle oil for a gallon of gas.

With technology continuously improving, manufacturers such as Honda began creating 4-stroke trimmers that do not need an oil/gas mixture.


During power outages, it’s very advantageous for homeowners to use their generators. It allows them to continue working or studying. Most generators use regular unleaded gas that has an octane rating of at least 87.

Remember to turn off the generator and let it cool for at least 2-3 minutes before filling up the tank. Do not refuel the generator while it’s turned on!

Snow blowers

Any homeowner during winter struggles with snow. Snowblowers help clear out roads and walking paths.

These tools use gasoline with an octane rating of 87. They do not need gasoline with higher octane ratings. Remember to stay away from fuel with ethanol contents of more than 10%. These tools can function with standard fuels with 10% ethanol.

Remember these to avoid corrosion in the engine.

Owning small engine equipment helps with different tasks at home and at work. Remember to buy the recommended fuel to avoid corrosion in the engine. Greg’s Small Engine helps you pick the right fuel for your equipment and maintain it.