Lawn Mower Engine Surging – Check this easy fix first. Motor for push mower

Lawn Mower Engine Surging – Check this easy fix first!

Lawnmower engine surging is a right pain in the Jacksie; it’s an engine that runs erratically and revs up and down by itself uncontrollably. In some cases, it may only happen under certain conditions, for example, only after the mower gets hot or only when the fuel level gets low.

So what causes the lawnmower engines to surge? The most common reason for a surging lawn mower engine is a blockage in the fuel supply, but there are other possibilities:

Often you’ll find playing around with the throttle helps or applying some choke. You are not on your own; this is a regular complaint. In this guide, we will cover the diagnosis, likely causes, and solutions.

Try the easy fix first – replacing/cleaning gapping the spark plug before attempting carburetor work. If your mower engine is a Honda or Kohler, the fix is simple. Honda and Kohler’s surging is commonly caused by a blocked idle jet see “Gas starvation” towards the end of the page.

If your surging mower is a Honda, check out the “Honda mower surging video.”

For many mowers, the fix is to replace the carburetor, and as carburetors are inexpensive, it just makes sense to swap it out and save a ton of messing around. You can check out the quality carburetors available and conveniently delivered to your door by

Briggs Stratton Surging

Surging BS Classic 450, 500, or 550Some engine types are famous for surging; the Briggs Stratton 450, 500, and 550 series engines are fitted with a metal fuel tank and priming bulb-style carburetor. If you have one of these types of engines and it’s surging – You’re in the right place.

If you don’t have this type of carburetor, skip this section and jump to “Surging Test” below. These engines are fitted with a metal fuel tank and carburetor combination. The gasket sandwiched between the tank and carburetor distorts over time, allowing a vacuum leak.

The vacuum leak causes the surging; replacing the gaskets and cleaning the carburetor/tank will leave it like new, I promise. In this tutorial, we’ll remove the tank/carburetor unit, clean it and replace the gaskets. Just some basic tools are needed, but get yourself a can of carburetor cleaner; it makes the job a lot easier.

In the workshop, I use WD40 carb cleaner, and you can check out all the tools and parts I use here on the “Small engine repair tools” page.

Tools You’ll Need

Here’s a short list of tools you’ll find useful to complete the task of fixing your surging mower. These tools aren’t essential, but they do make the whole job a ton easier; you’ll need:

Fuel treatment – Every small engine owner should use gas treatment. Most people don’t know gas goes off, and gas left in small engines can cause real problems, as you already know.

Using a gas stabilizer will keep the gas in your mower and your gas can fresh for up to two years.

Carburetor gasket – If you’re fixing the BS Classic engine, then you’ll need this gasket set.

Complete carburetor – As an alternative to replacing your BS Classic carburetor gasket, replace the complete carburetor instead; it includes the replacement gasket.

Manifold – This will only be needed if you have confirmed it has failed. Note there are a few different types of manifold pipe, so be sure to check before ordering.

You can check out all these tools on this page “Carburetor Surging Repair Tools.”

This carburetor style is fitted to a few engines and is prone to gasket failure. The job of replacing is simple and will solve the surge. The process is as follows:

Remove the spark plug wire – prevents the mower from starting.

Remove – Remove and clean the air filter and filter housing – Clean it using soapy water, and when dry, smear some engine oil over the surface of the foam. This helps trap dirt.

Remove tank bolts – They hold the fuel tank to the engine.

With fuel tank bolts removed – pull the tank unit straight out gently and remove the governor control link.

Remove the black rubber elbow crankcase breather pipe. Remove the manifold seal and keeper ring. Sometimes they will come loose and get stuck on the manifold pipe.

Remove – Remove carb screws from the carburetor and set aside.

Using a can of carburetor cleaner – clean all the ports on the surface of the fuel tank.

Empty the tank and rinse it out with fresh gas.

Pull the Siphon from the carburetor; they can be stubborn. Remove both gaskets and use carburetor cleaner to clean the siphon metal filter and all ports of the carburetor. Check the primer bulb for damage; mice like to eat them.

Spray – Spray the carburetor with carb cleaner.

Remove – Remove old gaskets and discard them.

Careful of this spring; it lives under the gaskets, and it can drop off and be tricky to find, as I know only too well.

The gasket is a two-part kit; the rubber-type gasket faces the tank. (carb fitted here for demo only)

The Siphon pushes back into the carb with a click. If you don’t hear the click, it’s not right – try again.

Refit the carburetor to the tank. Don’t over-tighten the screws, as this will distort the gasket. Fit manifold seal and keeper. Smear a small amount of oil on the seal; it helps it seat.

Clean the intake manifold. The grey tube in this shot is manifold. Inspect it for any signs of damage; they are prone to cracking. This will also cause a surge.

To fully inspect the pipe, you need to remove the pull assembly.

I would only do this if there was obvious damage to the manifold or if I had replaced the carburetor gasket and the engine was still surging.

This manifold is cracked and will cause a surge.

Before refitting the tank, fit the keeper ring and O-ring seal. Lube the seal before refitting the gas tank.

Offer the carb/tank unit up to the manifold and attach the governor link and spring. Now push the unit firmly onto the manifold. Fit both bolts.

Refit the air filter and spark plug wire. Use only fresh gas; make sure your gas can is clean. Gas older than three months is stale.

If, after fitting the gaskets, you still have a surge – Replace the Manifold.

Surging Test

As you know, gas starvation causes an inconsistent flow of fuel which in turn causes erratic running. And you also know a vacuum leak will cause erratic running, but it is a much less common cause; however, some carburetors are prone to vacuum leaks.

As engine manufacturers strive to make their engines more efficient, they have also made the carburetors more likely to clog; this has become a common issue.

To quickly diagnose which problem you have, a clogged carb or vacuum leak, follow this simple test.

You will need a helper to hold the bail lever or improvise with duct tape. CAUTION careful where you place your fingers and toes; the engine will be running, so the blade will be spinning.

Your mower will have a Manual choke, Auto choke, or a Primer bulb. Identify which type your mower has; the test is slightly different for each.

If you have a manual choke – apply half choke with the engine running.

If the engine now runs without surging – Gas starvation is the likely fault. If it runs just the same – A vacuum leak is a more likely fault.

If you have an Auto choke – Remove the air filter cover and filter – place a clean rag over the intake while the engine is running.

If the engine now runs without surging – Gas starvation is the likely fault.

If the engine runs just the same – A vacuum leak is the more likely fault.

If you have a primer bulb – you can still do the test – while the engine’s running (need a helper); give it some extra gas by pressing the bulb.

If the engine now runs without surging – Gas starvation is the likely fault.

If it runs just the same – A vacuum leak is a more likely fault.

Gas Starvation

If the test revealed gas starvation, it also showed that your problem is likely a dirty fuel jet in the carburetor, or the gas may be stale or contaminated by water.

Idle Jet Surging – Honda and Kohler use a relatively easy-to-access idle jet that clogs up and causes surging. The Kohler is easier to access than the Honda. Briggs has fitted a plastic carburetor to a range of engines which also clog up and cause surging.

All of these carburetors can be repaired by cleaning. It’s all covered in the video library. It shows you step by step how to remove, clean, refit, and adjust your carb. It’s a detailed, engine-specific guide, easy to follow, and only regular tools are needed.

Fixing this is not difficult. Sometimes you can get lucky by just draining and cleaning the gas bowl, which only takes a few minutes. I have written a complete guide to Carburetor cleaning with pictures; it includes the gas bowl clean-out, which is worth trying first.

If cleaning doesn’t work out for you, go ahead and swap out the carburetor for a new one. Check out “New lawn mower carburetors page,” here, I’ve listed good quality replacement carburetors for all the most popular engines.

Carburetors aren’t so inexpensive; messing around with them doesn’t make sense.

You might find this page helpful, too – “Carburetor repair tools” I’ve listed some really useful tools that make the job easy. Some of these tools I’ll bet you already have some.

But do try cleaning the gas bowl before removing the carburetor.

Finding a Vacuum Leak

Air that enters the combustion chamber without passing through the carburetor is un-metered. This means the fuel-to-air ratio is unbalanced and, in turn, causes erratic engine performance.

When air sneaks in like this, it causes the engine to run lean (lacks gas). A lean engine runs hot, which isn’t good for an engine, especially an air-cooled one.

Vacuum leaks usually occur because of damaged gaskets. Gaskets are sealing materials fitted between the mating surfaces of engine components. Their function is to create an airtight seal.

They are commonly made from paper, felt, cork, Teflon, neoprene, metal, and rubber. The material type is dependent upon where the gasket is to be used.

Gaskets wear out and break down, and that causes surging.

Extreme Caution – You need to be careful, the engine will need to be running, and so the blade will be spinning when running this test.

A vacuum leak check is performed with the engine running and a can of carburetor cleaner; WD40 works, too, (is there anything WD can’t do?)

Spray the cleaner around all carburetor gaskets anywhere the carburetor meets the engine. The trick is to hear an instant change in engine note; that’s the sign of a vacuum leak.

This can be challenging; you must train your ear to notice the instant change in engine note (and not the surging).

Just do a small section at a time; this will allow you to pinpoint the failure area. Jumping the gun and replacing gaskets without finding the actual leak may work out for you or leave you with the same problem after the rebuild. You’re right in thinking carburetor gaskets usually cause the problem, but other components, such as manifold pipes, can crack or become loose, causing surging.

Fixing A Vacuum Leak

If a leak is detected, replace all carburetor gaskets, and as you have the carburetor removed, go ahead and clean it. Replacement gaskets are available online; you will require the make and model numbers from the engine.

All manufacturers will have a model number printed on a sticker placed on the body or on the engine. Have a poke around; you’ll find it. Most engine manufacturers will stamp the model numbers in an accessible area. Briggs Stratton stamp their numbers on the metal engine cover.

A new carburetor comes with new inlet gaskets; I like to fit original parts where I can; they fit and are guaranteed.

If, after replacing the carburetor gaskets, the engine still surges, you’ll need to go a little further and replace the manifold intake and gasket.

It’s not a big job, and they don’t give a lot of trouble, but they do crack as they get older. I wrote a step-by-step guide showing you everything you need to know – “Briggs Manifold Replacing.”

Related Question

Honda lawn mower surging fix? To fix a surging Honda lawn mower engine, clean the carburetor, gas tank, and fuel filter. Use fresh regular gas or e10. What causes a lawnmower to run slowly? The most likely cause is a throttle linkage bent out of shape by bumping into the shrubbery or a throttle spring has detached itself.

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.

Types of Lawn Mower Engines ( How They Work)

The first lawn mower was patented back in 1830 by a guy called Edwin Beard Budding in Stroud, England. It was a 19-inch reel push mower made of wrought iron that was mainly used to mow sports fields and cemeteries. Here we are, nearly 200 years later, still using a very similar design reel mower. But there have been many advances in mower technology, meaning we don’t have to use a steam engine or a horse to power our mowers. So, what lawn mower engines can you have? Let’s take a look.

Different Types of Lawn Mower Engines (The Short Explanation)

There are several power sources you can have to drive your modern lawn mower. These include the following different designs:

Types of Lawn Mower Engines and How They Work (A Closer Look)

To be honest, that is a much bigger list than I expected. There are a couple here that you don’t see too often and one that has only just become available. Let’s take a look.

No Engine Rotary Mowers

Ok, so this one we will all recognize. Even Edwin Budding would think this is a familiar design. Basically, it’s a mower without an engine. The reel lawn mower. This lawn mower uses the motion of the wheels to generate the power needed to turn the cutting blade.

Reel lawn mowers are great little lawn mowers for little yards. You’ll see reel lawn mowers made by manufacturers like Scott and Fiskars stacked on the shelves at the big box stores.

These mowers are great because you get a workout, there’s no noise, they’re pollution-free, and have no additional fuel cost.

Corded Electric Motor

Greenworks, Craftsman, and Black Decker are just some of the manufacturers making corded electric lawn mowers. Oh, and let’s not forget Flymo with their corded electric hover mower. These are lawn mowers that use a blade connected to an electric motor which is then connected to a power outlet via a long cable.

These are a pretty good choice of lawn mowers for smaller yards. Corded electric mowers have plenty of power and all the features of the traditional gas-powered lawn mower. On the upside, they are a lot quieter and don’t require the same servicing and repairs you’ll expect with a combustion engine. The only downside is that you’re limited by the length of the cable.

Battery Electric Motor

Battery-powered lawn mowers have been around for some time now. They use a battery to power their electric motor the same way a corded electric lawn mower would, but they’re no longer limited to the length of a cable.

These lawn mowers can tackle much bigger yards and can run for much longer. This is down to the fact that manufacturers such as Worx, Greenworks, and EGO Power are using much more powerful lithium batteries that can be up to 80v in a single mower.

So, you no longer have to deal with small 12v lithium batteries that struggle to get you even a quarter way around the yard.

Solar/Battery Electric Motor

Ok, so solar/battery lawn mowers are pretty new, and there are only a few currently available. But this is soon going to change because a particular state has already banned gas-powered lawn mowers and leaf blowers due to carbon emission targets. I’ll let you guess which state passed the ban into law. Hint: it’s on the west coast.

So, these are basically the same as battery lawn mowers, the only difference is these mowers have solar panels included within their design. You get the same features of a battery-powered mower with powerful electric motors and batteries, but you get the added feature of charging your mower with the power of the sun. Mean Green Mowers of Hamilton, Ohio, is just one of the manufacturers producing solar/batteries lawn mowers.

2-Cycle Gasoline Combustion Engine

The 2-cycle gasoline engine is a small engine you’ll find on most of your gas-powered yard tools. It uses the movement of a piston to turn a driveshaft and provide power to the cutting blade and the drive system of a lawn mower. The movement of the piston is generated by a small explosion in the cylinder head of vaporized gasoline, hence the name combustion.

The thing that makes a 2-cycle engine different from other engines is that oil is added to the fuel to lubricate the internal moving parts. So, are 2-cycle lawn mowers any good? Well, these smaller engines consume less fuel than a 4-cycle engine, and they are cheaper and lighter.

On the downside, they are limited in the amount of power they can produce and are pretty noisy. Companies like Briggs Stratton, a highly respected engine maker, produces 2-cycle engines for various lawn mower manufacturers.

4-Cycle Gasoline Combustion Engine

This 4-cycle engine is another combustion engine that works in the same way as a 2-cycle engine. The only difference is that this engine uses oil stored in a sump to lubricate the internal parts instead.

Now, if you are looking for the most popular lawn mower engine, then this is it. These engines start out pretty small, like 100cc, the same as a 2-cycle, but are also available in huge 1000cc models that will power even the biggest zero-turn and riding lawn mowers.

So, if you’re looking for better reliability or more power, then this is a great choice. Most lawn mower manufacturers like Toro, Husquvarna, John Deers, and Dixie Chopper all produce lawn mowers that use 4-cycle gasoline combustion engines.

You’ll see a variety of engine makers like Kohler, Kawasaki, and Honda all producing 4-cycle engines for the big-name lawn mower manufacturers.

4-Cycle Diesel Combustion Engine

Diesel engines on lawn mowers have been around for a long time in commercial and agricultural settings. But more and more manufacturers like John Deere, Walker, and Hustler are producing tractor lawn mowers and zero-turn lawn mowers with Diesel engines.

This is because diesel combustion engines have better fuel consumption, are stronger and longer-lasting, and require less maintenance and less servicing compared to a 4-cycle engine. So, diesel is a huge improvement over gasoline.

LPG/Propane Combustion Engine

These are basically the exact same engine as the 4-cycle engine, but instead of having a gasoline tank, they have an LPG/Propane cylinder. The only real mechanical difference is that the carburetor is designed to be fed with gas, not liquid.

What’s the benefit of LPG? Well, the cost of the LPG and the reduced carbon emissions. So, you can pick up an LPG push or ride-on mower from manufacturers like Green Gear or Exmark, or you could convert your existing gasoline lawn mower over to LPG.

Is One Type of Lawn Mower Engine Superior?

If you were to compare all these lawn mower power choices out in an open field, then there would be a clear winner. But this isn’t going to help you unless you have a big open field. So, how do you know what type of lawn mower engine is going to best suit you and your yard? Well, you need to see which mower uses which engine and suits your yard size.

Fixing a surging Briggs & Stratton motor.

Which Engines are Available on Which Lawn Mowers?

Engine TypeReelRobotPushRide-OnZero-Turn

Which Mower Suits your Lawn Size?



About Tom Greene

I’ve always had a keen interest in lawn care as long as I can remember. Friends used to call me the “lawn mower guru” (hence the site name), but I’m anything but. I just enjoy cutting my lawn and spending time outdoors. I also love the well-deserved doughnuts and coffee afterward!

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Types of Lawn Mower Engines

You can buy any type of lawn mower. But buying the best type of mower for your property, is a little more difficult. In this article I’ll introduce you to the most popular types of lawn mower engines, how they work, and help you decide which type of mower might be best for you.

Choosing the Best Mower for You

How necessary is a riding mower when you’ve got a small lawn?

Lawn Mower Surging Causes

Should you choose a walk-behind mower with auto-choke?

What’s the best way to keep your mower running smoothly for years to get the most out of your investment?

Choosing a lawn mower comes with a lot of questions, and while I won’t get into or answer every one of those questions in this article about the different types of lawn mower engines, I hope you’ll stick around to explore other relevant articles on my blog.

First, consider the size of your property. Also, consider your level of physical fitness.

If you don’t have a large property you probably shouldn’t buy a riding lawn mower, unless you have a bad back or other physical limitations.

If you have a massive property with many different trees, gardens and planting beds, a high-end zero turn mower or lawn tractor might be best.

Once you try this electric zero turn mower from Greenworks you’ll never look at battery powered tools the same way again.

  • Mows up to 2.5 acres in a single charge.
  • Fully charged in 90 minutes.
  • Equivalent power to 24 HP gas engine.
  • Quiet, no fumes, and faster than competitors (8 MPH max speed).

Type of Lawn Mowers and Their Engines

Now let’s dig in and get to know the various types of lawn mower engines and the mowers they power.

Push Mowers and Push Mower Engines

The sound of a lawnmower starting up with the yank of its pull cord.

One of the most familiar sounds on a summer morning in the suburbs.

Most lawnmowers you see in the suburbs and smaller lots are probably walk-behind or push mowers. This is one of my favorite types of lawn mower.

Push mowers, in general, allow you to direct the mower whichever way you want, manually. You have control to stop instantly by releasing the throttle (which needs to be held down to keep the motor running).

The Silent Walk-Behind Reel Mower

Reel mowers are eco-friendly, quiet, cost-effective and much easier to maintain.

They run off no engine and offer a more efficient lawn cut. They work best on smaller lawns, and are not ideal on steep lawns or hilly yards.

With reel mowers there’s no need for gas or oil changes, they are as basic as it comes, and they’re good for the environment.

Big yards need big attention and that’s exactly what lawn tractors provide.

lawn, mower, engine, surging

Also known as lawn and garden tractors, these riding mowers are great for larger properties you find on larger lawns. Riding mowers have steerable wheels to provide strengthened maneuverability. The offer you the ability to cut your lawn while being comfortably seated.

Lawn Tractors

Garden Tractors are capable of pulling attachments or using snowblowers to manage a multitude of tasks on your property in any given season.

They are a heavy-duty alternative to traditional tractors if you’re looking to do more than tidy up your lawn.

Zero Turn Lawn Mowers

Zero-turn lawnmowers are riding mowers that provide great performance. They use four-wheel steering to complete sharp turns and move around any objects and obstacles like trees, garden beds, and landscaping boulders. Drivers can raise blades and control speeds much easier with these mowers and, to be frank, they’re lots of fun to drive.

Engine Types – Typically around 14 horsepower engines

Maintenance – These mowers take a lot more gas and oil, which should be expected due to their size and the fact that they can handle a heftier workload.

To keep your riding mower running smoothly, follow your manual instructions on your specific model and ensure that you check underneath the deck after every couple of uses to ensure there isn’t any damage.

To avoid injury, refer to an expert to check underneath the deck if you’re not confident to do so since these mowers are often very large and heavy. Always make sure your mower is turned off and the key is removed.

Cost – Riding mowers typically start around 1,000, but high-end zero turn mowers can cost upwards of 10,000 depending on the horsepower engine and features.

Zero-turn mowers are often the most expensive and the latest models with all the bells and whistles (what landscapers will buy) can cost 12,000.

Hover Mowers

You may have never heard of hover mowers before, but they do exactly as advertised – well, sort of. They are extremely mobile and use rotating cutting discs to cut your grass. Air is trapped underneath the deck to create a lift, making it lighter and easy to move around.

I don’t consider these an everyday option, and if I’m honest I personally don’t care for hover mowers, but if you have a very small yard and like unique tech, then you might love one.

Engine Type – Both two-cycle and four-cycle engines, depending on the model

Maintenance – To keep it running smoothly, follow your manual instructions on your specific model and ensure that you check underneath the deck after most uses to ensure there isn’t any unexpected damage.

Cost – These can cost as low as 50 to as high as 1,000 or more.

Robotic Lawnmowers

Yes, it’s time! Automated machines have made their way onto our lawns. What the Roomba has down for vacuuming, robotic mowers are now doing for suburban yards around the country.

Sit back and relax while your robotic mower does all the work of mowing your lawn. Your weekends are now free, and you can enjoy a healthy, freshly cut lawn every day of the week.

You manage the boundaries of the mower by installing a boundary wire which restricts where and how far the mower will roam (you don’t want it cutting the neighbor’s lawn, right?).

lawn, mower, engine, surging

The set up is not as easy as regular mowers, but once you’re set up you can pretty much ignore your robotic mower for the rest of the season.

Engine type – These have several different types of engines, but most of them are battery-powered and have a docking station that they return to to recharge when their battery begins to get low.

Maintenance – Because these are robotic, much of the maintenance has to be done carefully to ensure the mower is completely powered off. To keep it running smoothly, follow your manual instructions on your specific model.

Cost – You should expect to pay 1,000 or more for a high quality robotic mower that will last.

Engines up!

Lawnmowers and cars have a lot in common. If you’re familiar with your car and the type of engines out there, this is just a rehashing of what you already know.

For those out there not too familiar, however, I’ll quickly cover the common types of lawn mower engines.

For starters, the cylinder number refers to the total number of pistons in the engine. The pistons move vertically inside the engine, opening and closing the air intake valves to combine air with fuel for combustion. The air and fuel combust, which provides power to the engine.

In general, the more pistons an engine has, the more powerful the lawn mower engine will be.

  • Two-CycleTwo-Cycle lawnmowers aren’t as optimal as their counterparts and often require pre-mixing of oil and fuel. This type of lawnmower engine is sometimes found on small mowers, weed eaters, and other small pieces of lawn and garden equipment. They are lighter to use and are best for smaller jobs.
  • Four-CycleThe more common type of lawn mower engine is the four-cycle engine. Often better on the environment and more efficient than two-cycle lawnmower engines, they have more parts, do more work, and last longer. Unfortunately, due to having more parts, these lawn mower engines require more maintenance (though with proper maintenance, they’ll last longer).

Auto vs Manual Choke Lawn Mower Engines

Last, but not least, does your lawnmower use an auto choke or manual choke?

Manual choke lawnmowers incorporate a little push valve or dial located near the engine to give your mower optimal starts by being pushed several times. Auto-choke lawn mower engines, however, do this automatically and don’t require the same attention and function by being automatically opened and closed.

Auto choke mower engines are designed to save you time. Old-fashioned manual choke engines tend to be less prone to engine issues, so it’s what I typically recommend if you want a mower that will work for years without issue and are new to owning lawn equipment. That said, my auto-choke self-propelled Honda mower works great. I’m not sure how much stock I put into the engine issues for auto-choke lawn mower engines.

Sorting Through the Best Types of Lawn Mower Engines Mower Types

No matter what type of lawn mower engine you choose to cut your lawn, pay attention to your budget, your lawn, and your abilities.

Don’t tire yourself in the process of creating a wonderfully cut lawn and don’t take a shortcut to save a few dollars. Invest in an appropriately sized, highly reviewed mower.

What Type of Lawn Mower Oil Should I Use


Your lawn mower needs the right kind of engine oil used in the right way. Read on to learn about different lawn mowers and the oil they need.

Our editors and experts handpick every product we feature. We may earn a commission from your purchases.

Why Lawn Mower Oil Matters

Like all internal combustion engines, lawn mower engines need oil to run. Even simple engines have many moving parts, often designed to work at extremely high speeds and temperatures. This is why the lubricating and cooling action of oil is essential. Without it, your lawn mower’s engine would quickly overheat, seize and be ruined.

Lawn Mower Oil Types

Motor oil comes in different grades, based on viscosity and how the oil behaves at different temperatures. Most mowers have what are called four-stroke engines. This means they burn straight gasoline as it comes from the service station pump, but they also require motor oil to be added separately to the crankcase of the engine. 10W30 is a common motor oil grade suitable for many lawn mowers. Your owner’s manual will tell you the exact grade required, but in almost all cases 10W30 is the right stuff for a four-stroke engines.

Any brand of oil that’s suitable for cars or trucks will work fine in your mower. All reputable oil includes a service rating in addition to a viscosity rating. Look for oil that’s designated SF, SG, SH, SJ or higher.

  • Single Grade Oil: A single grade level oil typically without additives to change its viscosity and represents only at higher temperatures (100°C).
  • Multi Grade Oil: A multi grade level oil that uses additives to provide better viscosity at a range of temperatures.
  • Synthetic Blend Oil: A mixture of regular and synthetic oil with additives to help perform at colder temperatures without the cost of a full synthetic oil.
  • Full Synthetic Oil: An artificially created lubricant with a wide range of benefits designed for use in high performance and commercial engines

Some lawn mowers have two-stroke engines, and these require oil in a different way than four-stroke engines. All two-stroke engines burn gasoline and oil at the same time. In the case of lawn mowers, two-stroke engine oil is mixed with the gasoline before it goes into the tank. Mixing ratios of gas to oil vary, but usually range from 30:1 (4-1/4-oz. of oil to one gal. of gas) to 50:1 (2-1/2-oz. of oil to one gal. of gas). The owner’s manual for your lawn mower lists the mixing ratio of gas to oil.

Two-strokes are becoming less common because of emissions regulations, but they’re still around. How do you know if you’ve got a two-stroke or four-stroke engine in your lawn mower? Your owner’s manual is the best source of guidance.

How to Choose the Right Lawn Mower Oil

Family Handyman

Some experts say that more expensive “small engine oil” is the only type of oil you should put in your mower with a four-stroke engine, but that’s not true. Standard engine oil made for cars and trucks is the highest quality available today and it works optimally with all four-stroke engines. Got a two-stroke engine? Any two-stroke motor oil made for air-cooled engines, such those in chainsaws, water pumps and weed eaters, will work perfectly in your two-stroke lawn mower engine.

  • SAE 30 Oil: Engine oil best suited for warmer temperatures. Try top rated Pennzoil SAE 30 Motor Oil.
  • SAE 5w-30 Synthetic Oil: Synthetic mower oil good for warm and cold weather use. Try top rated Castrol Edge 5W-30 Full Synthetic Motor Oil.
  • SAE 10w-30 Synthetic Oil: Synthetic oil that can help in colder temperatures. Try top rated Mobil 1 Advanced Full Synthetic 10W-30 Motor Oil.
  • SAE 15w-50 Synthetic Oil: Synthetic oil typically used for high end and commercial engines. Try top rated Mobil 1 Advanced Full Synthetic 15W-50 Motor Oil.

The best way to mix gas and oil for a two-stroke engine is to put the required amount of oil into your empty gas can, then go to the gas station and fill it up. Before using the mixed gas, give the can a shake to so the oil and gas are properly mixed.

What is Synthetic Oil and Should I Use It In My Lawn Mower?

Synthetic oil is superior to lubricants made from crude oil, and your lawn mower engine may last longer if you use synthetic. Essentially, it is a synthetic lubricant made up of chemical compounds designed to give engines the performance and protection that natural oil may not be able to provide. According to Briggs and Stratton, one of the world’s largest manufacturers of small engines, the use of synthetic oil does not alter required oil change intervals. Regular, non-synthetic oil works well, too. I’ve used non-synthetic in some of my small engines for 30 years, and these motors still start and run as if they were new.

How Often to Check and Change Lawn Mower Oil

Only lawn mowers with four-stroke engines have oil that can be checked and changed. Tuning up a lawn mower at least once a season, which includes changing the oil, is essential for maximizing fuel economy and extending the life of the engine. Aside from that:

If your four-stroke engine lawn mower is new, change the oil after the first three to five hours of use. As parts of a new engine wear initially, the internal movement of parts releases tiny metal filings into the oil that will cause excess wear if left there.

  • Walk-Behind Mowers: Change oil in mower at least once a season or every 50 hours of use.
  • Riding Mowers: Change oil in mower at least once a season or every 100 hours of use.
lawn, mower, engine, surging

The owner’s manual for your lawn mower lists the amount of oil required, but you’ll do fine following the dip stick or oil level mark that’s part of every four-stroke lawn mower engine.

How to Check Lawn Mower Oil

Before each mowing session, you should check your lawn mower’s oil level and top it off if necessary. To do so:

  • Place your lawn mower on a level surface and let it sit idle for a few minutes so that the engine oil can settle.
  • Remove the oil cap and wipe the dipstick off with a clean cloth. Put it back into the oil tank and tighten the cap.
  • Once again, remove the cap and check the oil level on the dipstick. The level should fall between the “full” and “add” marks. There may be differences in the appearance of these marks depending on the brand of mower you own. Some dipsticks may have only two holes to indicate “full” and “add”, or a cross-hatched pattern. Either way, you want the oil level to be between the two holes or marks. As close to the “full” side as possible without exceeding it.
  • Whenever more oil is needed, add it in small increments and repeat this process between each addition to prevent overfilling the engine.

How to Change Lawn Mower Oil

When looking to change the oil in a lawn mower, follow these steps to check off this simple and easy maintenance check.

How Much Oil Does a Mower Take?

Depending on the make and model of lawn mower, push mowers have an oil capacity ranging between 13-1/2-and 22-ounces and riding mowers between 48-and 64-ounces. A mower’s operator’s manual will always list the proper amount of oil recommended for its engine.

What Does SAE Stand For in Oil?

SAE is the acronym for the Society of Automotive Engineers. They are an organization that sets global standards in a variety of fields related to transportation and aerospace. It is the responsibility of the SAE to ensure that automotive oil is standardized throughout the world.

Can You Use Car Oil in a Lawn Mower?

Yes. As previously stated, engine oil made for cars and trucks is the highest quality oil on the market and it works optimally with nearly all four-stroke engines.

Steve Maxwell is an award-winning content creator who has published more than 5,000 articles, shot countless photos and produced video since 1988. Using his experience as a carpenter, builder, stone mason and cabinetmaker, he has created content for Mother Earth News, Reader’s Digest, Family Handyman, Cottage Life, Canadian Contractor, Canadian Home Workshop, and many more. Steve lives on Manitoulin Island, Canada with his wife and children in a stone house he built himself. His website gets 180,000 views each month, his YouTube channel has 58,000 subscribers and his weekly newsletter is received by 31,000 subscribers each Saturday morning.