Lawn mower side shoot. Mulching vs Side Discharge: Which One Wins As The Best Lawn Mower

Mulching vs Side Discharge: Which One Wins As The Best Lawn Mower?

Mulching vs side discharge compares the two most commonly used lawnmowers today. On the one hand, you have mulching mowers that can mulch and fertilize grass while cutting it simultaneously.

On the other hand, you have side discharge ones that allow you to cut wet, long grass and cover a large area. Find out the basic differences between both of them in this well-researched guide.

• Mulching vs Side Discharge Comparison Table
• What Is The Difference Between Mulching and Side Discharge?
• What Are The Characteristics Of Mulching Mowers?

• – Serves As a Fertilizer
• – Needs Less Cleanup Afterwards
• – Safer Than Side Discharge
• – Makes The Grass Look Lush
• – Not Good for Wet or Long Grass

• – Mows Large Areas Quickly
• – Can Be Used On All Soil Types
• – Works Even On Wet and Tall Grass
• – Less Frequent Mowing Needed
• – Side Discharge Is Very Messy
• – Waste Of Grass Clippings

• – Should You Mulch Every Time You Mow?
• – Do You Have To Mow Slower When Mulching?
• – Will Mulching Weeds Spread Them?
• – Why Does My Mulching Mower Leave Clumps Of Grass?

What Is The Difference Between Mulching and Side Discharge?

The main difference between mulching and side discharge is that mulching types have curved blades that cut grass into very small pieces. There is no opening for discharging the lawn cuttings. A side discharge has an opening through which it throws the clippings out.

What Are The Characteristics Of Mulching Mowers?

Some important characteristics of mulching are that it serves as an effective fertilizer. needs less clean up, and makes for a healthier lawn.

– Serves As a Fertilizer

Mulching blades help you to fertilize your lawn while you mow it simultaneously. What happens is that they cut off the grass finely, and then the cut grass moves into the cutting deck. where it is chopped up into different finer pieces.

These very finely cut pieces of grass are then strewn across the lawn while the mower moves from one end to another. These are naturally rich in nitrogen and serve as organic mulch and fertilizer.

Because they are cut into such small pieces, they get decomposed in a short amount of time. In many ways, this natural fertilizer works much better than any organic fertilizer. What is even better is that these clippings are laid down in a neat little layer that does not ruin the overall look of the lawn.

– Needs Less Cleanup Afterwards

Unless you live someplace very windy, using mulching types of blades will need very little cleanup after mowing. If tall buildings surround your lawn, then the mulch clippings will be automatically prevented from being blown away by strong winds.

The grass cuttings laid over the lawn by these blades are pretty neat and do not give a rough appearance. However, if you still want to clean up your lawn after mowing. that is quite easy.

over, these mowers have the option of turning off the mulching mode as well. You can simply choose to collect the grass clippings instead of converting them into mulch or discharging it from the side.

– Safer Than Side Discharge

These mower blades are much safer compared to side discharge blades. This mower keeps all the clippings contained under the body of the mower.

This means no more cut grass pieces flying off the sides. This is handy when people and pets are around, and you do not want pieces of grass going into their eyes.

– Makes The Grass Look Lush

Using mulching blades to mow the lawn and simultaneously spread grass clippings as mulch over it will make your lawn lusher. Mulch acts as an organic layer over the entire lawn, which prevents excessive water from evaporating. In fact, mulch can help retain as much as 80 percent of water. compared to grass that is not covered by mulch.

So basically, these grass cuttings not only help retain water but provide nutrition as well. You will notice your grass becoming greener and lusher than ever.

However, remember that only grass varieties with wide blades take kindly to being mulched. Do research on what grass variety you have growing on your lawn and whether you should mulch it or not.

– Not Good for Wet or Long Grass

Mulching mowers are not suitable for cutting wet grass. When cut into small pieces by such blades, wet grass gets stuck inside the cutting deck and is not discharged by the mower.

Unless you clean the deck after each use, these wet and clumped-up clippings will also affect the efficient working of the mower blades.

over, the curved end of the mulching blade does not give it the freedom to cut very long grass either. Again, using this blade to cut long grass will lead to the deck clogged and random long pieces of grass collecting patches over the lawn.

What Are The Characteristics of Side Discharge?

Some important characteristics of side discharge are that it can quickly mow grass in very large areas of land, is suitable for all soil types, and, most importantly, will even cut tall and moist grass.

– Mows Large Areas Quickly

A side discharge mower is great for mowing lawns that are large in size. This mower will do the work much faster if you allow the cut grass to blow in various directions.

This mower is much faster because it does not have to spend time converting cut grass into mulch. The mower just keeps cutting ahead with its sharp blades and discharging the cut pieces on the side in a very short amount of time.

– Can Be Used On All Soil Types

A discharge mower has the great advantage of working on all soils, lawns, and grass types. Do not worry about it if your lawn is made up of a mostly sandy type of lawn.

Still, the grass blades need to be taller if this mower is to cut them efficiently. You will find it hard to mow grass that does not grow very tall.

The surface of the lawn is also better flat or smooth for discharge to work properly. Otherwise, the grass will get cut up unevenly.

– Works Even On Wet and Tall Grass

Compared to mulching mowers, discharge ones are very effective against wet or tall grass. This is because they have an opening on the side from which the lawn clippings get thrown out. These wet or long clippings will not get stuck within the blades or cutting deck.

This is good news for you because you will not have to clean your mower after each use. You will also not have to wait for the rainwater or the early morning dew to dry before embarking on lawn mowing.

If you do not have time for regular lawn care or your grass seems to grow tall quickly, then this is the mower you need to have. The shape of the side discharge blade allows you to cut wet and tall grass easily compared to that of a mulching type of blade.

– Less Frequent Mowing Needed

A discharge mower will save a lot of time because less frequent mowing will be needed. Firstly, this is because it can mow very tall grass without any risk of it getting choked up. The grass can grow tall whenever you are busy and then be easily cut off when you get the time for it.

Secondly, the side-discharge mowers are designed so that their blades can cut very close to the ground. For grasses that can be mowed low, this is very useful.

You can mow them as low as possible and take a break until the grass grows again. We are sure that those who live hectic lives or are not that invested in constant lawn care will be very happy with this feature.

– Side Discharge Is Very Messy

Side discharge basically works by splattering grass clippings several feet away from the mower. Because of how the blades work, these clippings are strewn in all directions, making your lawn look messy.

Walls and fence that might be lining the lawn will get their fair share of grass splatters. If wet grass is cut, it will literally stick to any surrounding boundary or car parked alongside the lawn or the turf.

You will also have to ensure no one is around when cutting grass with side-discharge lawn mowers. Humans and pets might cut grass into their eyes, which can be quite harmful.

– Waste Of Grass Clippings

Honestly, using side discharge instead of mulching mowers seems like a waste of grass cuttings. The grass cut by side-discharge type blades is much too large to serve as an effective fertilizer.

over, these clippings are randomly strewn over the lawn and serve no purpose. In fact, they sometimes look so bad that they need to be removed from the lawn after mowing.

Some of the latest mower types allow you to bag grass clippings and store them. This will save you from cleaning the lawn after mowing, but you will still have to deal with the bagged clippings by yourself.

Frequently Asked Questions

– Should You Mulch Every Time You Mow?

It is unnecessary to mulch your grass every time you mow, but it is beneficial. Mulching types of mowers are great because they give you the option of either turning cut grass into mulch or bagging it for any other use.

If you mulch grass every time you mow, you will see a great improvement in the condition of the lawn. A layer of mulch will help retain more moisture during hot days. decompose quickly, and turn into fertilizer.

– Do You Have To Mow Slower When Mulching?

Yes, you have to mow slower when mulching grass while mowing. A mulching-type blade must cut grass clippings multiple times to become a worthy mulching material. Naturally, it cannot do so if you use the mower at a very high speed.

With this mower, you need to go slowly also because it gets clogged up easily. Grass cuttings have no escape when the side discharge opening is closed. If you are going too fast, you risk getting the cutting deck clogged much faster.

– Will Mulching Weeds Spread Them?

Yes. mulching weeds will spread them all over the lawn. During mowing and mulching, the weed seeds will also get converted into mulch along with the grass blades.

These seeds will then be spread all over the lawn by the mower along with the mulch. Soon, you will notice weeds erupting where they were not growing. That is why we do not recommend mulching unless your lawn is completely weed-free.

– Why Does My Mulching Mower Leave Clumps Of Grass?

Your mulching-type mower is probably leaving clumps of grass because you are mowing wet grass. This mower is not designed to mow wet grass efficiently.

Not only does it leave clumps of grass behind, but that machine also gets clogged.

Conclusion

You have now read a great deal about the mulching vs side discharge types of mowers. The main difference between them lies in their design and blade shape.

If you have a small lawn with grass that will grow better when mulched, then a mulching type of mower will suit you the best. For larger lawns and grass that grows tall frequently, a side discharge type of mower might be a better choice.

My Lawn Mower Chute Clogs – Solved!

Just so FRUSTRATING!! Cutting tall, heavy grass, especially if it’s wet, will keep you busy clearing the chute all day.

So what’s going on? Why does my mower chute clog? The most common reason a mower chute clogs are because the grass is too heavy, but there are lots of other reasons:

Lawnmower grass catcher troubleshooting is straightforward; most are common problems and easy to solve. In this guide, we’ll look at all the most common causes.

Grass height, weather conditions, and a worn blade will be the most obvious reasons for the tractor or walk-behind mower clogging. Very often, a dull, damaged, or worn blade is the root cause of a clogging chute.

If you need video help, check out the “Mower blade sharpening video” it walks you through the whole process step by step, from examining the blade, sharpening both on and off the mower, blade removal, blade balancing, refitting, including using a torque wrench to tighten blade bolt to spec.

Conditions Chute Clogging

As a guide, you should cut no more than 1/3 off a blade of grass at once. For best results, a mower shouldn’t be cutting more than an inch of grass, and the best lawn height is about 3″. Cutting regularly keeps the workload on the machine to a minimum, and it’s easier on your lawn.

Weather makes a big difference. Obviously, if the grass is damp, the mower is going to struggle to perform. But I understand, sometimes it’s necessary to cut wet grass when you need to get the job done.

A clogged chute can, of course, is a symptom of an underlying problem. Clearing the chute may not resolve the issue. Grass build-up or damage to the underside of the deck can cause the grass to catch and clog. The underside of the deck should be smooth so that the grass moves freely around the deck, up the chute, and into the bag.

Chute – Clearing the chute may not solve the problem. Check the chute for damage or old dry grass build-up.

Clean – Old grass on the deck can cause problems. Regular cleaning will prevent build-up and prolong the life of your mower.

Deck Wash Port – Clean the underside of the deck at the end of the season, as the acid in the grass eats away at the metal over the winter. Most mowers will have a garden hose connection on the deck, simply connect your hose and run your blades to clean the underside of the deck. This does a reasonable job of cleaning.

The wash-out port isn’t fitted to all mowers. It does a pretty good job of cleaning the underside of the deck.

Hose – Move your mower to a suitable location, as it leaves a bit of a mess. Just attach and turn on a garden hose. Start your mower to engage the blades. Run until the water runs clear – simple!

Deck Coating – After cleaning the deck and allowing it dry thoroughly, spray on a coat of WD40; it’ll help protect the deck over the winter and also help keep the deck grass-free in the spring. Better than that is applying a non-stick film, it works pretty well, and it’s easy to apply.

The best in the business – DuPont Teflon non-stick dry film, and you check out the price on Amazon.

Clean – Lift the front of your tractor, and secure it well before climbing under. A wire brush and paint scraper do the job.

To Prevent Clogging

To help prevent clogging, three options are common:

Option 1 – Quick fix is to spray the deck with WD40. It does help, but it won’t last.

Option 2 – Spray deck with DuPont Teflon coating.

Option 3 – Spray the deck with bed liner. Works on tractors, riders, and walk-behind mowers. Check out the video here.

Check Your Grass bag

A clogged grass bag is a common problem. Tractors and walk-behind mowers often get cleaned at the end of the season (well, some do), but bags rarely do. Symptoms of a clogged bag are not collecting or only a half-filled grass bag.

Examine your bag/box; when held to the light, you should be able to see through it. A stiff brush will remove the old grass, or use a power washer.

Consider buying a new grass bag if damaged. They are available to purchase, usually with or without the frame. Check if the bag/box sits correctly against the mower body. If it’s loose, the air and grass flow to the bag will leak.

Bag – Thatched grass on the inside of the bag is a common issue. It prevents airflow through the bag, which in turn prevents grass from entering the bag.

Clean – As a rough guide, you should be able to see through the bag. A stiff brush or, better, a pressure washer does a great job.

Check For Blade Damage

Two types of blades are common, the lift blade and the mulching blade. They are fitted to tractors, ride-on, and walk-behind mowers. A defective blade can cause vibration, uneven cutting, and poor grass collection.

No need to tell you a bent blade is dangerous and should never be repaired. A new blade, bolt, and washer is the way to go.

Examine – Check your blades for damage, misalignment, or bent or broken tips. Your blade is the business end of the mower and needs to be in top condition. Defective blades can cause vibration, uneven cutting, and poor grass collection. A mowing blade may look OK, but they do wear.

Mowing blades are engineered to cut and move grass; as they wear, they become much less efficient. A worn blade will cause clogging.

Timed Blades – Some deck setups will have an overlapping cut, although more common on lawn tractors than walk-behind mowers.

Toro Timemaster walks behind the mower and has a timed blade set up. To achieve this, the blades must be fixed at a set angle in relation to each other. This is done by using a toothed timed belt.

If one of the blades hits an object, the blades go out of time, or the belt can break. When the blades are out of time, bagging quality suffers, and a clogging chute is a symptom. In addition, badly timed blades usually damage each other. I wrote this detailed guide, including pictures, to help you replace your “Timed deck belt”.

Dull or Worn Blade

A dull or worn blade will cause clogging; as the carefully engineered blade wears, the trailing edge is less efficient at moving the clippings. The leading edge will also be worn from grit and debris, and sharpening sessions will likely have changed its shape.

The average mower should get a new blade every 3rd or 4th season. If the blade is in good overall condition, go ahead and sharpen it.

Lift Blade

The Lift blade is also known as the 2 in 1, so-called because it bags and discharges. Lift blades vacuum the grass upright, before cutting and moving the clippings to the bag. Lift blades are specially designed for collecting grass and come in the low, medium, and high lift.

2 in 1 Lift Blade

Lift means sucking power; a higher lift blade will require a more powerful engine. The lift is created by curving upwards of the trailing edge of the blade.

If you like bagging – You need a lift blade.

Mulching Blade

A true Mulching blade is designed to cut grass, circulate it around the deck, cut it several more times, and drop it back onto the lawn as fine clippings.

You’ll know a mulching blade when you see it; the leading edge isn’t straight; it curves up and down. This results in several cuts to the same grass blade but at different heights – fine clippings.

If you’re not interested in mulching, then remove the mulching blade and fit a lift blade. It will always bag better than any hybrid mulching blade.

3 in-1 Blade

A true Mulching blade is not designed to collect. That got engineers thinking – Meet the hybrid mulching blade or 3 in 1. It attempts to do it all, mulch, bag, discharge. However, we all know it can’t be excellent at everything, and it isn’t.

Mulching has become quite popular, and manufacturers have responded by making a blade that tries to do it all but doesn’t quite succeed.

Check out the blade replacing video here, and if you need new blades, check out the Amazon link below.

Engine Performance Problems

It’s also worth considering if the throttle is set correctly; it should be set to fast/run when cutting. Is the engine running as it should? If the engine power is reduced, the mower may still cut well but will be less efficient at collecting.

A small-engine tractor or walk-behind mower should have a tune-up at the beginning of every season, regardless of how well it might be running.

I wrote these guides to help you tune up your own mower; it includes an oil grade chart and quantity for your engine; check out:

Bad Gas

Stale gas is the number one most common cause of poor engine performance. It’s usually caused by letting gas sit in the mower over the winter. The bad gas can damage the carburetor causing 100 in repairs, and it’s not covered by your warranty.

This problem can be avoided by using a gas stabilizer; you won’t have to use it all season, just at the tail end. It’s simple to use, just dump the bottle of gas stabilizer into your gas tank and run the engine to mix it throughout the fuel system, that’s it. You can find a link to the fuel stabilizer I use here and a video on how to use it here.

The fix for bad gas – is to remove and clean the carburetor; if it’s badly corroded, you’ll need to replace it.

I wrote these easy-to-follow guides, including pictures on carburetor cleaning, which will help you find your problem and fix it fast.

Tune-up – Mowers like a tune-up at least once per season.

What Is Power Take Off (PTO)?

The PTO clutch assembly will not be fitted to all mowers, and so this may not be applicable. It’s fitted mostly to tractors, ride-on, and larger walk-behind mowers.

A PTO clutch is a unit fitted to the end of the crankshaft. The deck belt wraps around the PTO pulley; its function is to apply the power of the engine to the blades when a switch or lever is operated.

PTO Wear

The PTO clutch, when worn, will slip, reducing power to the blades. This will be especially noticeable in taller grass. The PTO, if fitted, will be manual or electromagnetic.

If manual, it will likely have a lever and cable to operate – check that the cable is pulling the PTO. Both types can’t be repaired; they must be replaced.

PTO – Check the PTO system. The manual version is engaged by a cable. It lives on the crankshaft, right under the engine. Check that the cable is pulling the PTO lever all the way.

Fitting – Replacing the PTO isn’t difficult; air tools make it look really easy.

Tractor Belt Wear Problems

Belt wear is also a common reason for a chute to clog; check the deck-cutting belt for damage and general wear tear. A new belt will transfer more of the engine power to the cutting blades and will improve the cutting and bag-filling performance.

Belt types and lengths will be specific. Some brands will only work well using OEM (Original Equipment Manufacturer) belts.

Worn – A cutting deck belt that’s slipping will be less efficient at collecting. Check the belt for proper tension, cracking, glazing, or contamination.

Damaged – Damaged belts will cause vibration and poor general performance. A typical deck belt might last 3 – 4 years.

You may find these links useful:

Related Questions

Why is my lawnmower spitting out grass? Common reasons for grass trailing is grass-bag or box not sitting on the mower deck correctly. Check for gaps around the bag/deck interface and holes in the bag.

Grass not going into the lawnmower bag? When your mower isn’t filling the grass bag, first try cleaning the bag, if that doesn’t help, replace the cutting blade.

Hey, I’m John, and I’m a Red Seal Qualified Service Technician with over twenty-five years experience.

I’ve worked on all types of mechanical equipment, from cars to grass machinery, and this site is where I share fluff-free hacks, tips, and insider know-how.

And the best part. it’s free!

So which is best mulching vs bagging vs side discharge?

It’s no secret, there are many ways to handle lawn clippings.

And, with all choices, there are pros and cons for each method.

But don’t worry, we made things simple with this guide.

Let’s take a look!

What Do The Pros Say?

We surveyed 880 of GreenPal’s lawn care pros to see which grass clipping management method that they preferred.

Of the 880 Respondents:

• 620 said they preferred to mulch the clippings.
• 180 said they preferred to use side discharge.
• 80 said they preferred to bag them.

According to our survey 70% of lawn care professionals prefer to use a mulching kit.

However, it is important to note: One big reason more lawn care professionals do not use a bagging system instead, is that many clients are simply unwilling to pay more for the time involved.

However there is much more to the story!

Method #1- Bag Your Clippings

The first method we will mention is the second most common method for handling grass clippings among homeowners. Use a bagging attachment on your lawn mower.

Look, bagging lawn clippings is simple.

Install a bagging system on your mower, and all you need to do is find a place to dump the clippings.

importantly, there are huge benefits to bagging your grass clippings including; the ability to cut grass in nearly all conditions, and best of all it can remove weed seeds from the lawn.

If you do bag your grass compost your clippings!

• Can help reduce weeds by removing seed heads from the lawn.
• Provides the most professional appearance.
• Works even when the lawn is wet.
• Remove all debris from the lawn such as grass clippings and leaves.
• Less likely to throw a rock or other object which can cause damage.
• Takes longer due to having to dispose of the grass clippings throughout the mowing process.
• You need to have a place for dumping grass clippings.
• Removes free nutrients from the lawn.
• Requires a lawn mower with high enough HP to cut effectively.

Bagging in a Nutshell

Hands down, bagging grass clippings is the all around best method for most homeowners, especially if your lawn is full of weeds or not that well established.

But that is still not the whole story.

Method #2- Use the Side Discharge

Perhaps the most popular among homeowners is using the side discharge.

For many homeowners the side discharge works just fine, and since it is the default for most mowers, most simply use this method.

Best of all, cutting tall grass is not a problem.

Using the side discharge is easily the fastest method to use.

• Mowing tall or wet grass is best done with a side discharge.
• Offers a good quality cut.
• Fastest mowing speed.
• Throws clippings everywhere.
• Less powerful mowers can leave clumps of grass in the lawn which can leave brown spots.
• Can throw seeds and grass into flower beds.
• Anything that gets under the mower deck can be shot into cars, homes or people.

Side Discharge in a Nutshell

Side discharge is good overall, and provides a fast, quality cut. IF you mow very regularly.

However, there are some significant downsides to using a side discharge system, including throwing grass and other debris everywhere.

But what about mulching?

Method #3- Mulch the Grass

Most people don’t know this, but there is a 3rd lawn mowing option, and that is mulching the grass.

Get this, this type of mulching has nothing to do with the mulch you use in a garden bed.

Instead, mulching grass involves a closed mower deck and mulching blade.

Rather than discharging grass. Mulching mowers chop up the grass, and even leaves, into tiny pieces which quickly break down into the lawn.

Now, there are some downsides to mulching the grass. The biggest problem is that tall grass can be difficult to cut.

Additionally, low HP mower may not have the power required to mulch the grass properly.

• Little or no visible grass clippings.
• Keeps nutrients in the lawn.
• Non-stop mowing.
• Can mulch fall leaves into the lawn.
• Less likely to throw a rock or other object which can cause damage.
• Not ideal for wet or tall grass.
• May add to thatch build up.
• May encourage disease in the lawn.

Mulching in a Nutshell

Mulching is a great all around option for homeowners that cut their lawn regularly.

Not only does mulching keep nutrients in the lawn, mulching also reduces the risk of throwing a rock or other object into a car, home or person.

Bottom Line on Side Discharge vs Bagging vs Mulching

The way you should handle your lawn care clippings greatly depends on your individual goals and lawn.

Using this infographic on how to handle lawn clippings can help you decide which grass clipping method is best for you.

Best of all, if you don’t feel like taking the time to figure it all out, reach out to the pros at GreenPal, and they will handle it for you!

Hi, I’m Gene Caballero and I’m the co-founder of GreenPal. At GreenPal, we’re helping hundreds of thousands of Americans solve one of the trickiest problems: a reliable, fast, and affordable way to get lawncare taken care of. On behalf of GreenPal, I’ve been featured in the Indianapolis Star. the Sacramento Bee. Entrepreneur. Inc.com. and dozens more. Please feel free to say hi on or connect with me on LinkedIn.

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.