2 Stroke vs 4 Stroke
Buying garden equipment is, for most, a weighted decision. You are buying equipment that, with the right treatment, will last you many years so making the right decision is paramount. When getting your equipment set up there are no blanket rules about what is the best, however, you need to weigh up your requirements and choose the features that suit you best.
If you’ve decided to purchase your equipment in the petrol category (rather than battery or electric powered) you need to make an additional decision… do I want a 2 stroke or 4 stroke engine?
In this post we are going to discuss some of the features of both and encourage you to consider all the different features when making up your mind. Keep in mind that there are 2 and 4 stroke engines in outdoor power equipment but you can also use the following information to inform your decision about motorcycles and go karts as they also often feature both engine types.
I’ve worked in a retail mower business for 4 years now and grew up with a father who was in the industry for at least 30 years. Customers come in daily that are staunchly in favour of 2 or 4 stroke engines and often when probed are unsure why. When I meet these customers the “Pot Roast Principal” immediately comes to mind.
A story of 3-4 generations of women who cut the end off their roast meat. As they trace down the line from mother to daughter to enquire as to the reasons behind wasting this end meat each woman explains that they do so because their mother did the same. They finally trace back to a great grandmother who explains her oven was too small to fit the entire roast and that’s the only reason she would cut off the end. Needless to say, generations of women wasted countless kilos of meat based on their mother before them without ever thinking to enquire about the reasons.
Customers will demand a 2 or 4 stroke engine because that is what their father, brother, neighbour or landscaper mate told them to do. However, your needs for your average sized block in the suburbs may be different to the land owner who owns a couple of acres in the country. It is paramount to make your own informed decision separate to the advice of those around you.
So, let’s weigh up the features of both.
Without getting too bogged down in the details it is important to understand a bit about these engines before proceeding with this breakdown. All engines cycle through a 5 step combustion cycle to create power. These steps are intake, compression, ignition, combustion and exhaust. To complete a cycle 2-stroke engines take two strokes of the piston (or one crankshaft revolution), whereas 4-stroke engines take four strokes/two crankshaft revolutions. With this in mind the first consideration is:
Generally speaking the power to weight ratio of a 2 stroke engine is better than a 4 stroke engine. 2 stroke engines will complete a combustion cycle twice in the time it takes for a 4 stroke engine to complete one cycle.
Due to the above as well as a 2 stroke’s ability to rev up to higher speeds and the use of exhaust ports (rather than valves) means less weight for more power.
2 strokes and 4 strokes reach ideal power in a similar way, however, 2 strokes generally create more power per cubic centimetre. However, 4 strokes provide more torque (rotational force) with no dips and spikes as 2 strokes do. 4 stroke provides smoother power while 2 stroke engines provide optimum and improved power but only under ideal RPM range mean the engine, where possible, sometimes needs to be modulated.
In summary 2 stroke provides lively, quick power while 4 stroke provides steady, consistent power.
In line with power, weight is an important consideration. Many people insist a bigger engine equals more power and this, for the most part, is true. Even so, a bigger engine also equals more weight and when you have to carry this weight in your hands you have to make a trade off between power and size. A 4 stroke engine can sometimes be up to double the size of a 2 stroke engine that generates the same power this, again, is because a 2 stroke is completing two functions per rotation instead of only one.
4 strokes are generally heavier, by up to 50%, due to additional moving parts in the engine. More weight can be favourable as it provides stability and as a result weight in an item like a lawn mower can be ideal. For equipment you have to carry, 2 stroke engines are a better option as they cause the user less fatigue and give them more manoeuvrability.
Fuel and Lubrication
Having worked in a mower shop for the past 4 years the number one turn off for customers regarding 2 stroke machines is having to mix fuels. For those that don’t know, 2 stroke machines have one fuel tank where you put a specific mixture of fuel and 2 stroke oil. While 4 strokes have a traditional set up similar to what you would see in a car where there is one compartment for fuel and one for 4 stroke oil.
4 strokes are lubricated by oil stored in the crankcase while 2 strokes are lubricated by the oil mixed into the fuel. One of the downsides to the 2 stroke mixtures is that much of the oil in the fuel is not burned in the lubrication process and ends up as an emission… in the simplest terms, 2 stroke engines generate more pollution.
In order to deem 4 strokes to be more environmentally friendly you must dispose of your motor oil correctly with a liquid waste service. If you change your oil and dump it down a sink or on some grass it is likely causing just as much harm as emissions from a 2 stroke.
4 stroke engines are generally more fuel efficient as they only consume fuel every 4 strokes.
Beyond considerations of the environment the mixing of 2 stroke fuel is not as complicated as some believe it to be. You will need to make a few one off purchases and a few ongoing purchases depending on how you set yourself up.
You will need a five litre Jerry Can that is used strictly for your 2 stroke equipment (don’t try and use one can for multiple purposes as you will eventually mix something up and nothing kills a 2 stroke quicker than straight fuel with no oil in it). Next you will need 100mL of 2 stroke oil.
Go to your local service station and put 5 litres of regular unleaded fuel into your Jerry Can (no ethanol - I’ll explain later). Add your 100mL of 2 stroke and give it a shake every time you need to fuel your machine just to move the oil around and that is it!
It honestly only is about a 3 step process and 5L of mixed fuel will probably fill the tank 7-10 times.
Most quality 2 stroke brands now mix at a fuel to 2 stroke ratio of 50:1, which is 20mL of 2 stroke oil for every 1L of unleaded petrol.
A hidden advantage to running a 2 stroke engine is every time you change or top up fuel your “changing the oil”. In a 4 stroke engine you should change your oil every 10-20 hours of use so this is just something you need to remember to do.
Motor Design and Maintenance
2 stroke engines have a simpler design with less moving parts than a 4 stroke engine. In the event of a breakdown a 2 stroke engine will require less parts at a lower cost, meaning maintenance is generally more expensive on a 4 stroke.
One thing I commonly hear about 2 strokes is that they are louder. However, according to research on decibels the sound produced by 4 stroke machines is a deeper sound that carries further and rates higher on a dB reading. The problem is 2 strokes produce a higher pitched sound which many find to be more irritating.
This isn’t much of a category because there are a lot of variables, especially depending on where you are reading this from. It’s difficult to compare apples to apples in terms of price as different brands and model types offer different features. Generally speaking you can get a 2 stroke model with similar power to a 4 stroke model for cheaper.
Some additional considerations that aren’t lengthy enough to warrant their own section.
A Simple Breakdown
2 Stroke: More power for less weight.
4 Stroke: More power for more weight.
Winner: Tied, you can get similar power in each type, it’s just how much weight you want to carry.
2 Stroke: 2 power strokes per revolution.
4 Stroke: 1 power stroke per revolution.
Winner: 2 Stroke.
2 Stroke: More dips and spikes.
4 Stroke: Better rotational force.
Winner: 4 Stroke.
Types of Power
2 Stroke: Lively and quick.
4 Stroke: Steady and consistent.
Winner: Tied, depends on your application
2 Stroke: Lighter.
4 Stroke: Heavier (sometimes up to 50% for the same power production).
Winner: 2 stroke (although a heavier machine may be better for applications where stability is required).
2 Stroke: Requires Mixing with 2 Stroke Oil.
4 Stroke: Regular Unleaded (oil in separate compartment).
Winner: 4 stroke (but only just, this simply depends on preference).
2 Stroke: No oil change required as oil is mixed into fuel.
4 Stroke: Every 10-20 hours oil requires changing.
Winner: 2 Stroke.
2 Stroke: Oil emissions are more significant.
4 Stroke: Minimal emissions.
Winner: 4 Stroke.
2 Stroke: Less moving parts.
4 Stroke: More moving parts.
Winner: 2 stroke (less parts = less to go wrong).
2 Stroke: Perceived as noisier as they produce a higher pitched sound.
4 Stroke: Technically noisier on a dB rating but don’t seem as annoying due to lower pitch.
Winner: 4 Stroke.
2 Stroke: Cheaper.
4 Stroke: More Expensive.
Winner: 2 Stroke.
2 Stroke: Easier
4 Stroke: Harder
Winner: 2 Stroke
2 Stroke: European countries such as Germany.
4 Stroke: Asian countries such as Japan.
2 Stroke: Can be stored most ways.
4 Stroke: Needs to be stored level.
Winner: 2 Stroke
When weighing up all the features I believe 2 strokes are a much better choice for handheld equipment such as blowers, trimmers and chainsaws. They are more powerful for less weight and less money. For applications where torque and stability are requirements a 4 stroke is a better choice, this, and the fact that 2 stroke lawn mowers are becoming harder to come by is why I would recommend a 4 stroke lawn mower.
Kibbe, M. (2014). The Pot Roast Principal. https://www.psychologytoday.com/au/blog/thinking-makes-it-so/201402/the-pot-roast-principle
Berryman Products. (?). What’s The Difference Between 2-Stroke and 4-Stroke Engines? https://www.berrymanproducts.com/two-stroke-vs-four-stroke-engines/
Benedict, L. (2005). 2 Stroke and 4 Stroke Engines - What’s The Difference? https://www.lsuagcenter.com/portals/communications/news/news_archive/2005/december/news%20you%20can%20use/2stroke-and-4stroke-engines--whats-the-difference#:~:text=In%20a%202%2Dstroke%20engine,two%20revolutions%20of%20the%20crankshaft).
Deboer, C. (2009). 2 Cycle vs 4 Cycle Engines - Which Is Better? https://www.protoolreviews.com/2-cycle-vs-4-cycle-engines-which-better/
Ride with the Knights. (2020). 2 Stroke vs 4 Stroke - Which Is Better For You? https://www.youtube.com/watch?v=Nt-dAN6qFWI
Honda Lawn Parts. (2018). Servicing Your Honda Trimmer. https://blog.hondalawnparts.com/servicing-your-honda-trimmer/