Blue gasoline lawn mower. Bad Fuel Symptoms

What Type of Gas Do Lawn Mowers Use? Regular or Premium?

For the best performance of your lawn mower engine, you want to make sure you use fresh, clean fuel with a gas stabilizer. Keep in mind that most ethanol-based fuels degrade over time and can lead to such as poor starting and performance of the mower’s engine. So, what type of gas is best for lawnmowers?

Both 2-stoke and 4-stroke lawn mower engines use clean regular unleaded gasoline with a minimum octane rating of 87 with 10% or less ethanol. You can also use premium gas with a higher octane rating, such as 91 and 93. Two-cycle mowers can use regular or premium gas mixed with good two-cycle engine oil.

What kind of gas do lawnmowers use?

The best gas to use in a lawn mower depends on the engine type. Most four-stroke engines use fresh clean unleaded gasoline with an octane rating of 87 or higher. You might opt to use gas that contains not more than 10% ethanol.

Mowers with two-stroke engines use fresh unleaded gasoline with an octane rating of 87 or higher but with an addition of high-quality two-cycle engine oil. Therefore, they can run on either regular or premium gas.

Overall, lawn mowers use octane gasoline that has the following qualities:

• Is fresh and clean;
• Contains a minimum octane rating of 87;
• Has 10% ethanol or less.

As such, both regular and premium unleaded gasoline is recommended for lawnmowers.

What type of gas to avoid for your lawn mower

While you can buy regular gasoline at your local gas station for use in your gas push lawn mower, only fuel with a maximum of 10% ethanol is recommended. Most gas stations sell fuel with up to 85% ethanol, which is not good for small engines such as gas lawn mowers, gas-powered lawn edgers, etc.

See the table below for the type of fuel to use and the type to avoid for small engines:

Is it okay to use premium gas in a lawn mower?

You can certainly use premium high-octane gasoline in your lawn mower. However, it is recommended that you check your mower’s manual before using premium gas.

Most engines are designed to use minimum octane-rated gasoline; therefore, anything higher than that can easily damage the mower’s fuel system. Additionally, in most cases, there are no benefits, yet premium gas costs 5 to 20 cents per gallon more than regular gas. You need a higher compression ratio to get the advantage of higher octane numbers.

That being said, there is no harm in using premium gas in your lawn mower but don’t expect that it will improve your mower’s performance.

Regular vs premium gas for lawn mower

If you are trying to decide what gas is most appropriate for your gas push lawn mower, the first step is to read your owner’s manual to see what gasoline the manufacturers require. It is advisable to stick to the manual because any defects arising from using the wrong gasoline breach warranty.

The next step involves the compression ratio of your lawn mower. For optimal performance, mowers with high compression ratios require high octane fuel found in premium gas. However, most mowers are optimized to run on regular gas.

Premium petrol has a higher octane rate meaning that less filler is added to the gas, thus making it purer. However, lawn mowers can run on lower octane gasoline; therefore, premium gasoline is unnecessary. So why pay more for premium gas when regular gas can serve your mower?

Premium gas has fewer additives, but you still need the same amount of gas to run your mower. This means that you are not using better gas because you will still use the same amount but pay more if you use premium gas.

Premium gas is most suitable for the winter season, while regular gas is most suitable for summer seasons.

There is no harm in using premium gasoline; however, I recommend that you use regular gasoline because it costs less and offers the same performance to your mower as premium gas would.

Recommendations and Considerations

While there are many types of fuel to choose from for lawn mowers and other small engines for yard work, you might want to stick to the manufacturer’s recommendations for the best performance. But that’s not all; other factors may also come into play when selecting the right type of gasoline for your lawn mower.

Here are some important recommendations and considerations:

Use 87-octane, 10% ethanol gas

As a rule of thumb, a minimum of 87-octane containing up to 10% ethanol is the recommended gas for lawn mowers. Ensure that the lawn mower gas type is fresh and clean, as these fuels degrade rather quickly. Using leftover fuel from last season before winter might not be a good idea.

Beware that gas stations today also sell gasoline with 15% to even 85% ethanol. These are not approved for use in small engines such as lawnmowers, edgers, weed eaters, etc. Always check before you pump for ethanol free gas for lawn mower.

No mixing gas with engine oil

Do not mix gasoline with oil if the manufacturer does not recommend it. Also, avoid modifying 4-stroke small engines to run on alternative fuels because it will damage the fuel combustion system of your lawn mower. Manufacturers do not cover such damages under their warranties.

Check the label or manufacturer’s manual to determine if you have a 2-cycle or 4-cycle gasoline engine to ensure the type of petrol your lawn mower uses.

High-altitude adjustment

A minimum of 85 octane gasoline is recommended at high altitudes above 5,000 feet to remain emissions-compliant. You may need high altitude adjustment for your engine if you live in a high-altitude region to maintain the optimum performance of your lawn mower on its recommended type of gas.

Without such an adjustment, you may experience decreased lawn mower performance, increased emissions, and increased fuel consumption.

If you’re in colder climates, you should consider consuming stored gasoline within that season to ensure you maintain the performance of your engine.

Use additives to reduce fuel degradation

Since gasoline at the pump contains ethanol, you want to keep it from degrading over time and also from damaging the components of your lawn mower’s engine.

Use the official fuel additive recommended by your lawn mower manufacturer to prevent corrosion caused by moisture in fuels blended with ethanol.

Verdict: What’s the Best Gas for Lawn Mowers?

The best gas to use in your lawn mower is that recommended by its manufacturer. The rule of thumb is that you can use either regular gas rated at 87 octanes or premium gas that’s rated higher at 91 or 93 octanes. Do not use more than 10% ethanol gas to avoid damage to the mower’s fuel system.

If the manual recommends premium gas, that’s the type of gas that will give you the best performance. If you use regular gas instead, the engine will be damaged after a while. On the other hand, if it requires you to use regular gas, you MUST use it.

In the absence of such a requirement, the best fuel for your lawn is gas:

• That has a minimum of 87 octanes.
• Fresh. Fresh lawn mower gas prevents varnish and gum formation.
• With up to 10% ethanol or 15% methyl tertiary butyl ether (read the labels on your products to know their content).
• That is canned. Canned gasoline combines ethanol-free unleaded gas with a fuel stabilizer to prolong its life. Canned fuel products such as Briggs Stratton advanced formula ethanol-free fuel are suitable.
• Low octane rating for the summer season.
• High octane rating during winter.

The best gas to use for your lawnmower is the one that is required in your owner’s manual to avoid damage and breach of warranty. However, if your manual does not require any gas, you can use any octane gas with a minimum rate of 87 and available at a refilling station.

Does high-octane gasoline enhance performance?

Higher octane in premium gas will not enhance your mower’s performance, but it is not harmful. You should use it during winter but ensure you have cleaned out your engine before you change gasoline.

Regular gas is cheaper and ensures performance; it is best for summer. You may choose either but consider their prices.

Your biggest concern should be the amount of ethanol that is present in the gasoline. Lawn mowers need a maximum of 10% ethanol in their gas, so anything above that will corrode your engine.

It is better to buy canned gas like Briggs Stratton’s advanced formula ethanol-free fuel because you can analyze its ingredients and see its ethanol content. It also comes properly mixed and ready to use.

Pro tip: Do not mix oil in gasoline or modify your mower’s engine to run on alternate fuels. It might cause damage and void your manufacturer’s warranty. Avoid using leftover fuel that has been kept for more than 30 days.

I’m an degree holder in Urban and Horticultural Agriculture. My passion for landscaping and gorgeous lawns is undying. I’m confident that through Lawnmodel’s website, I can offer you some valuable insights and tips in lawn care and establishment.

Bad Fuel Symptoms

You make your way to the garage or shed, ready to tackle the day’s yard work, only to find that your lawn mower won’t start.

Did you know that bad gas is one of the most frequent causes of small engines not starting? Read on to learn about how to diagnose and treat engines affected with bad gas.

How long can gas be stored before it goes bad?

Whether in a gas can or in your mower, gas can go stale and lose its volatility in as little as 30 days. Using Sta-Bil Storage Fuel Stabilizer can increase storage time up to 24 months. Of course, many factors contribute to how long gas can be stored, including storage location, temperature, condition of the fuel container, and more.

What are the symptoms of bad gas?

If your lawn mower is difficult to start, idles roughly, stalls out, or makes a “pinging” sound, you may have a case of “bad gas”. And no, we’re not talking about the after-effects of dinner at your favorite Mexican restaurant.

How can I tell if the gas has gone bad?

The easiest way to diagnose gas is to smell the fuel in question. Oxidized gas has a sour smell and is much stronger smelling than fresh gas. The other method is to drain a sample from your machine’s fuel tank or your gas can into a clear glass container. If the gas is dark in color, it has more than likely gone bad. See the image below for a comparison between the color of fresh gas (Left) to gas that has oxidized (Right) and should not be used in your equipment.

Note the color of fresh gas (Left) compared to gas that has oxidized (Right)

What should I do if my equipment has bad fuel?

The best solution is to drain the gas from your equipment and replace with fresh gas. Remember to properly dispose of the old fuel.

How can bad gas affect my lawn mower?

If fuel was stored in the unit for an extended period, areas such as fuel lines and the metering needle may have become gummed up from the old fuel mixture. As gas ages, hydrocarbons in the fuel mixture evaporate and the remaining fuel becomes tacky or varnish-like. This can cause deposits and blockages in your equipment’s fuel system. In severe cases, professional cleaning of the carburetor and a possible carburetor rebuild are the only cure for this situation.

To verify this condition, remove the spark plug(s). If you can’t smell fuel in the combustion cylinder or see or smell fuel on the bottom of the spark plug, the fuel passageways are likely obstructed. If the carburetor is clogged, the use of spray carburetor cleaner and pressurized air may clear the obstruction. If this fails, then you should contact an experienced engine service center to have the system professionally and thoroughly cleaned.

Get the Parts and Tools You Need to Maintain Your Equipment Here at MTD Parts!

Spark plug wrench or socket tool (common sizes are 5/8, 3/4 and 13/16)

Common Engine Issues and Solutions for Lawn Mowers

A reliable lawn mower is essential to maintain a healthy, well-groomed lawn. However, like any mechanical device, lawn mowers can experience some issues that may hinder their performance. Continue reading to learn more about some of the most common lawn mower problems and practical solutions to fix or prevent them.

Why is my lawn mower smoking?

If you notice smoke coming from your lawn mower, it is typically a sign of an underlying issue. One common cause is an oil leak. Check the oil level and review the mower for any visible leaks.

If you find a leak, replace the damaged gasket or seal and ensure the oil is filled to the appropriate level. Smoking can also occur from an overfilled oil reservoir. If so, drain the excess oil and refill to the recommended level. A dirty or clogged air filter can also cause smoking. Remove the filter, clean or replace it if necessary, and ensure proper airflow to the engine.

Why did my lawn mower lose speed while running?

Losing speed while operating your lawn mower can be frustrating. One possible cause is a clogged or dirty air filter. Restricted airflow to the engine can result in decreased performance. Clean or replace the air filter regularly for optimal air intake.

If it is not an airflow problem, another cause could be a worn-out or loose drive belt. Inspect the drive belt for wear, such as cracks or fraying, and replace it, if necessary, as well as check the tension of the drive belt and adjust it as per the manufacturer’s guidelines.

A dirty or malfunctioning carburetor can also cause speed issues. Clean or repair the carburetor to restore proper fuel flow and maintain a consistent speed.

Why did my lawn mower lose power while mowing?

Losing power while mowing can be caused by a few different things. One common cause is a dirty or clogged fuel system. Debris and sediment can accumulate in the fuel tank, fuel lines, or carburetor, obstructing fuel flow over time. Clean the fuel system thoroughly, replace the fuel filter if necessary, and use fresh fuel.

A worn-out spark plug may also cause your lawn mower to lose power. Remove the spark plug and examine it for signs of fouling or damage. Clean or replace the spark plug as needed to ensure proper ignition.

Finally, check the mower’s blade for dullness or damage. Sharpen or replace the blade to maintain efficient cutting performance.

Why is my lawn mower making unusual noises?

Unusual noises coming from your lawn mower can indicate an underlying problem. A common culprit is a loose or damaged blade. Turn off the mower, disconnect the spark plug, and inspect the blades for looseness or damage. Tighten any loose bolts or replace the blade if necessary.

Another reason for unusual noises could be a faulty or worn-out engine component. Check the muffler, spark arrestor, or other engine parts for signs of damage or malfunction. Tighten any loose connections or replace damaged components as needed.

Additionally, inspect the mower for any foreign objects lodged in the cutting deck or other moving parts, as they can cause strange noises.

How can I prevent some of these common problems?

Routine service and maintenance are key to avoiding common lawn mower problems. A few tips to consider are:

• Regularly check and clean the air filter to ensure proper airflow.
• Keep the cutting deck clear of debris to prevent any impact to performance or unusual noises.
• Follow the manual recommendations for oil changes and use the correct type and grade of oil.
• Inspect and sharpen blades regularly for clean and efficient cuts.
• Replace the spark plugs according to manual recommendations.
• Clean the fuel system and use fresh fuel to prevent clogs and fuel-related issues.
• Store the mower in a clean, dry area, out of the weather elements.
• Use proper John Deere parts for your equipment.

Where can I find lawn mower service near me?

Addressing common lawn mower issues promptly helps keep your mower in top shape to provide you with a well-maintained lawn. Whether it is troubleshooting smoking problems, loss of speed or power, unusual noises, or implementing preventative measures, the certified technicians at your local Koenig Equipment are here for all your lawn mower repair needs, regardless of the brand.

Contact your local Koenig Equipment or schedule service online at any time.

Lawnmower Won’t Start? Do this.

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.

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.

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.

A smoking lawn mower is never a good sign. Whether the smoke is blue, white, or black, here’s how to identity and address the issue without the help of a professional.

By Glenda Taylor and Bob Vila | Updated Sep 24, 2020 1:40 PM

We may earn revenue from the products available on this page and participate in affiliate programs.

Q: Recently, my mower started billowing smoke when I powered it up, so I shut it off immediately. Why is my lawn mower smoking? And is it a fire hazard? I want to know how to proceed so I don’t harm the machine.

A: Your lawn mower can emit smoke for numerous reasons—many of which don’t require the services of an expert. A homeowner can usually identify the reason for a smoking lawn mower by gauging the color of the Cloud coming around the engine, then fix it accordingly before lasting damage occurs. Keep in mind that all mowers with internal combustion engines contain the same basic parts, but the configuration of those parts varies widely, depending on manufacturer and model. Consult your owner’s manual if you’re unsure how to access a specific part of your lawn mower’s engine.

White or blue smoke may indicate an oil spill on the engine.

If you’ve recently changed the oil in your mower and the engine is emitting white or blue smoke, it’s possible that some of the oil spilled onto the engine. Similarly, you could’ve spilled oil on the engine by mowing on a slope greater than 15 degrees or tipping the mower on its side. The smoke may look disconcerting, but it’s completely harmless. Solve the problem by restarting the mower and allowing the spilled oil to burn off. If you tip the mower often for cleaning or maintenance, check your owner’s manual to determine the best way to reduce the risk of oil leaks.

An overfull oil reservoir may also cause white or blue smoke.

Ensure you didn’t overfill the mower by checking the oil level with the dipstick located on the reservoir. To do this, remove the dipstick cap, wipe off the stick with a rag, and reinsert it into the reservoir. Then remove the dipstick once again and determine the oil level in comparison to the recommended “fill” line on the stick. If the level is too high, drain the oil (consult your owner’s manual for instructions), then refill the reservoir with it. Start checking the oil level with the dipstick after you’ve added about ¾ of the amount recommended in the manual. Continue to add small amounts of oil until the level matches the recommended “fill” line. Also note that using the wrong grade of engine oil may cause blue or white smoke. Consult the owner’s manual for the exact type of oil recommended for your mower.

Black smoke may indicate that the mower is “running rich,” or burning too much gasoline.

Your lawn mower’s carburetor regulates the ratio of gasoline to air mixture. If the carburetor isn’t getting enough air, the mixture has a higher percentage of gasoline, which can create black exhaust smoke. It’s possible that a dirty or clogged air filter is preventing sufficient airflow into the carburetor. Try replacing the air filter. (Note: air filters vary by mower model; view example air filter on Amazon.) Next, run your lawn mower for a few minutes. If the black smoke still appears, the carburetor might need to be adjusted in order to increase airflow. Either take the mower to a professional or adjust the carburetor yourself with instructions in your owner’s manual.

Take your mower to a repair shop if necessary.

If the previous steps don’t correct blue or white smoke, your mower could have a more serious problem, such as an air leak in the crankshaft (the cast iron or cast aluminum case that protects the moving parts of a mower’s engine). Continuing blue or white smoke could also indicate that some of the engine’s components or seals are worn out and need replacement. Similarly, if black smoking still persists after you’ve replaced the air filter and adjusted the carburetor, you could be facing a more serious mechanical issue. All of these problems require the help of a professional. If your mower is still under warranty, check with the manufacturer for the location of the nearest servicing dealer; problems stemming from a factory defect or poor workmanship may garner free repairs. If your mower is not covered under warranty, a reputable small-engine repair shop should also be sufficient to get the job done.