Are All Lawn mowers 4 Strokes? What Happened To 2 Strokes?




Are all lawn mowers 4 strokes?

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Are all lawn mowers 4 strokes?

Types of lawnmower engines.

They all cut your lawn but there are different kinds of engines that you will find on a lawnmower. 

  • A four-stroke 
  • A two-stroke

Both engines have their pros and cons but one engine is starting to dominate the market and the other is getting harder to find. 

Are all mowers four-strokes? While most mowers are four-strokes, two-stroke mowers still exist. However, newer mowers are more likely to be four-strokes as two-stroke models are being phased out globally due to emissions concerns and are unavailable in many countries. To identify your mower type, check for an oil dipstick – if present, it’s a four-stroke.

I remember as a kid watching my dad mow our lawns with his own little ecosystem of blue smoke floating around him and the mower. He was using a two-stroke mower. 

Nowadays you are much more likely to see someone out with a four-stroke but what made them so popular?

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So why are most lawn mower engines four-stroke?

There are a few simple reasons for this.

No need to mix fuel – This makes it easier to gas up your machine when you need it. You can just tip the gas in and go. Try that with a two-stroke and you will size the engine.

They use less fuel – Because the engine runs at half the RPM it uses less fuel so they are cheaper to run. 

A four-stroke is a quieter engine – The benefits of this are obvious. 

Fewer carbon emotions –  Due to the efficiency of the engine and the fact that it has no oil in the fuel a four-stroke engine runs a lot cleaner. 

Four-stroke engines last longer – A four-stroke engine runs at half the RPM (revolutions per minute)  than a two-stroke which equates to less wear and tear on the engine. 

This is the best explanation  I have seen of the difference between the RPM on both engines.

The 2-stroke at 3,600 rpm is firing 3,600 times a minute the 4-stroke at the same rpm is only firing 1,800 ties a minute. The 2 stroke sounds busier because it has twice as many power strokes at the same rpm. more power strokes more power

Benefits of a 2-stroke engine

Before you go thinking that all two strokes are bad, I should mention some of their good points.

Two-strokes are more powerful  – A faster blade does a faster cut. A two-stroke will do a better job on an overgrown lawn for the same reason.

They are easier to fix – fewer moving parts and because they have ports instead of valves. They also have fewer parts.

They are lighter than four-strokes – They produce the same power using half the weight. This is probably why most weed eaters, hedge cutters and blowers run two-stroke engines. (now modified to meet the new world emission standards) 

They are better mowers for slopes over 20 degrees – You are not going to have the same issues as a four-stroke, such as flooding the air filter or muffler with oil. You will also not get that lack of power when mowing up a hill that you would normally get with a four-stroke. 

You can flip a two-stroke on its side to clean underneath – This makes it super easy to clean your blades and is something you would not want to try with a four-stroke. 

Two strokes are cheaper – Normally they cost a little bit less than their four-stroke cousin. 

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2-cycle vs 4-cycle Lawn Mower: How do they work?

I have already written about this subject so to save me from repeating myself this is an article that covers how 2 stroke and 4 stroke engines work. 2-cycle vs 4-cycle Lawn Mower: Which is Better?


Ways to spot the difference between a four-stroke and a two-stroke engine. 

Apart from the dipstick, there are a few more ways to tell what kind of mower you have.

A Four-stroke has a separate oil reservoir. 

A two-stroke sometimes has the oil mix written on the fuel cap. 

Look for a sticker on the engine saying “Do not mix fuel” or “Four-cycle”. This means you have a four-stroke

This is an image showing the difference between the combustion cycle of a 2 stroke and a 4 stroke engine. 

What is the difference between two-stroke and four-stroke fuel?

Two strokes need oil in the fuel in order to lubricate the engine this is one of the main reasons that they have such high emissions. 

Here is a Ratio chart from Briggs and Stratton that should help you work out your mix if you have a two-stroke. 

Four stokes take straight unleaded gas so they are easy and less messy to fill.

If in doubt and you really need to get a job done you can use two-stroke gas in a four-stroke mower. It will smoke a bit, but as a one-off, it shouldn’t do any damage to the engine. You cannot use straight gas in a two-stroke as it needs the oil to keep the engine lubricated. Running a two-stroke with straight gas will seize the engine. 

Watch out for the fuel you use.   

While we are talking about lawnmower fuel, there is something that I should mention. A few years ago I became aware that some gas stations were starting to mix ethanol with their fuel. I had to actually tell my guys not to fill up at certain gas stations. 

Technically you can use up to 10% ethanol but now some gas stations are starting to use 15% so it’s a case of reading the label carefully. 

I myself avoid any fuel with ethanol in it when it comes to my mowers. Better safe than sorry I say. 

Also, there is a limit of at least 87 Octane for a lawnmower engine so don’t go any lower than that. I tend to use 91 myself and I haven’t had any issues. 

I did at one point use a budget gas station and I had a lot of engine issues all of a sudden so do be aware that not all fuel brands are created equal.

I would stay away from budget brands. 

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Why Are 2 Stroke Engines Banned in The US?

two stroke engines have either been banned or are in the process of being banned in the US. This is mainly because of their higher emissions of pollutants, the most common being hydrocarbons and particulate matter. 

Because they have a different combustion process the a 4-stroke engine they produce more emissions. This has raised concerns about environmental and public health.

There are now emission standards put in place by the Environmental Protection Agency that limit the environmental impact of this kind of engine. A lot of manufacturers has moved toward producing 4 stroke engines or direct-injection 2-stroke engines that meet these stricter emission standards.

Choosing the right lawnmower for your needs 

Factors to consider when deciding between a 2 stroke or 4 stroke lawnmower.

Power and Performance;

 Two Stroke; Generally two stroke engines are known for packing power into a size. They tend to be lighter and have designs, which can result in power-to-weight ratios.
 Four Stroke; While four stroke engines may be slightly heavier they usually offer more consistent and smoother power delivery. They also tend to be more fuel-efficient and quieter compared to two stroke engines.

2 stroke engines can be louder compared to their 4 stroke counterparts.

Fuel Efficiency

 Two Stroke; Two stroke engines typically consume fuel because they require a mix of oil and gasoline. However modern two stroke engines with fuel injection have seen improvements in fuel efficiency.
 Four Stroke; In general four stroke engines are more fuel efficient as they have systems, for oil and fuel.



 Two Stroke; Historically two stroke engines have been associated with levels of pollutants being emitted.These considerations should help you make a decision based on your needs. However, the progress, in technology such as fuel injection has played a role in reducing emissions in certain models of 2 stroke engines.Regarding 4 stroke engines they typically emit pollutants making them more environmentally conscious.


For 2 stroke engines they generally have a design with moving parts. However, they may require upkeep, including the mixing of oil and gas.
On the hand 4 stroke engines usually have an intricate design but often need less frequent maintenance. They have an oil reservoir which eliminates the need for fuel and oil.

Ease of use;

2 stroke engines are often lighter and easier to handle. They are commonly found in hand-held equipment.
In contrast, while 4 stroke engines may be slightly heavier they are generally more user-friendly and suitable for lawn mowers.

Conclusion: Are all lawn mowers 4 strokes?

In the end, the ideal choice will vary based on your preferences the size of your lawn, and how willing you are to handle maintenance tasks. If you value emissions, fuel efficiency, and a quieter operating experience then a 4 stroke lawn mower might be more suitable, for you. However, if you prioritize a power-to-weight ratio and simplicity, in usage then a 2 stroke mower could be an option to consider.

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