String trimmers are known by many names (Weed Eater is actually a brand name). If you are looking to buy a gas-powered model, there are two different types of gasoline engines available: 2-cycle and 4-cycle.
2-cycle and 4-cycle string trimmers each have advantages and disadvantages depending on your priorities and needs:
- 2-cycle weed eaters tend to be lightweight, easy to maintain, and affordable but are louder and not environmentally-friendly
- 4-cycle weed eaters are usually quieter and produce lower emissions but they tend to be more expensive and heavy.
The pros and cons will be discussed in detail, as well as how 2-cycle and 4-cycle engines function. Each engine has positive and negative aspects that need to be considered before you invest in a weed eater.
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What Is the Difference Between 2-Cycle and 4-Cycle String Trimmer Engines?
2. Easy To Maintain
|1. Not Environmentally-Friendly|
3. Gas and oil must be mixed at a specific ratio
2. Lower emissions
3. Don’t have to mix gas and oil
|1. Higher cost|
2-cycle and 4-cycle engines are sometimes referred to as 2-stroke or 4-stroke engines. This type of engine isn’t specific to weed eaters; chainsaws, edgers, and other gas-powered yard tools use these types of engines too. Regardless of the brand or type of yard tool, they will have the same basic combustion process that makes them run.
Both types of engines are powered by gasoline. The 2-cycle and 4-cycle engines are specific to gasoline engines. There are electric yard tools, but those engines function differently and don’t have the same stroke processes as gasoline engines.
How 4-Cycle Engines Work
The 4-cycle engine has several moving parts. It has a crankshaft, camshaft, a connecting rod, multiple valves and lifters, and a piston. It also has four basic stages that are completed in two revolutions, which is why it’s called a 4-cycle or 4-stroke.
The four cycles of a 4-stroke engine are:
- Intake stroke
- Compression stroke
- Power stroke
- Exhaust stroke
Each stroke, or cycle, completes one part of the 4-cycle process (source).
How 2-Cycle Engines Work
The 2-cycle engine goes through the same process but with fewer steps and has fewer parts. A 2-stroke only has a crankshaft, a connecting rod, and a piston.
It only takes one revolution to provide power, release exhaust, intake air, and compress that air. When the piston goes down, it creates power and releases exhaust. When it moves upwards, it takes in air and compresses it.
Because it can do the same amount of work in fewer strokes, 2-cycle engines create a more powerful machine. They are smaller than the 4-cycle engines because they don’t have as many pieces and don’t weigh as much.
How Are 2-Stroke And 4-Stroke Engines Lubricated?
Engines have to be lubricated so they can continually run smoothly. If they don’t get lubricated, they can wear out faster.
2-cycle engines use a mix of gasoline and oil in the same chamber. As the gasoline moves through the engine, the oil moves along with it and lubricates all the parts. 2-cycle engines typically require a specially formulated oil that you mix with gasoline.
Too little or too much oil can damage the engine, so be sure to read the manual that comes with the weed eater to find what ratio you need.
Note: 2-cycle oil can go bad so be mindful of how old it is when adding it to gas.
4-cycle weed eaters have separate compartments for oil and gas, so technically you can use the same kind of gasoline you use in your car for your weed eater, however, it is extremely important that you use gas with 10% or less ethanol to avoid damage.
I’ve grown partial to skipping the pump and using an ethanol-free fuel (link to Amazon). Ethanol-free gas is a great solution for gas-powered yard tools and allows you to completely avoid the moisture issues that cause so many issues.
You will also have to have oil in the second compartment. Since the oil and gas are separate, you will have to change out the oil. A good rule of thumb is to change the oil after twenty-five hours of usage. Most people that I know usually change the oil once a year at the beginning of the season.
The Pros and Cons of 2-Stroke and 4-Stroke Yard Tools
Before you make a purchase, you should consider the pros and cons of each engine. Each one has features that make it a valuable tool. But, they also have their downsides.
The key aspects to be compared are weight, power, fuel efficiency, noise levels, maintenance, and price. Each aspect is an important part that should be considered when making a purchase. Not every favorable aspect can be present in a weed eater, of course, so you need to decide which are most important to you.
Here’s the short and sweet of it. Read on for details on each section.
Feature Comparisons Between 2-Stroke and 4-Stroke Engines
If you are buying a weed eater for personal use, you may prefer the cheaper one that weighs less and is easy to carry around and handle. If you are a landscaper, you might prefer the fuel-efficient weed eater that will be able to run longer and cut through gas easier. Think about how you will use your weed eater as you read through each of these pros and cons.
Because 4-cycle engines have a longer process that uses more parts, the engines are typically bigger, which results in a heavier weed eater. A heavy machine can be difficult to maneuver, so you might end up with uneven lawn edges, especially if you’re teaching your child how to properly use it.
Many 4-cycle weed eaters need to be kept level so the oil will continually lubricate the engine. If they are tilted to the side for too long, the oil can’t be evenly distributed, and it will have the potential to damage the engine. If the weed eater is too heavy for the user, this might be a difficult task.
2-cycle weed eaters are lighter because they have fewer parts inside, so it should be easier to handle. You’ll be able to have better precision and get straighter edges on the lawn if you’re not struggling to carry for extended periods of time.
The 2-cycle weed eaters don’t have to be kept level. Since the oil is mixed with the gas and has a different lubrication system, it can be held at any angle. This will also make it easier to handle since you don’t have to worry about how you hold it. This might also be beneficial if you have a uniquely shaped lawn with difficult angles.
The 2-cycle weed eater has the advantage if you want to purchase a weed eater that the whole family can use since it’s lighter and easier to handle.
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Torque is the power that’s created by the engine that causes the blades of the weed eater to turn. 4-cycle engines produce more torque, giving you more power to work with. Because of the torque, 4-cycle weed eaters can cut through grass easily. If you have a particularly thick patch of grass, you will get through it quicker with a 4-cycle weed eater rather than a 2-cycle. 2-cycle weed eaters should still be able to get any job done, but you may have to work a little harder for it in some areas.
Since 4-cycle weed eaters are heavier, its power is beneficial because it will allow you to spend less time with the machine since it can cut through grass faster. If you have to spend more time with the lightweight 2-cycle weed eater, you may feel the same amount of fatigue as if you had used a 4-cycle.
4-cycle weed eaters have the advantage if you want to glide right through the grass and get the job done quicker.
4-cycle weed eaters burn cleaner and do not create as much pollution. The 4-cycle doesn’t cause as many fumes while the engine runs as the 2-cycle weed eater does. Since the gas and oil are kept separate, it doesn’t burn oil as it burns the gas, so you’re getting more usage out of the fuel.
Since the 2-cycle weed eater keeps gas and oil together, it will burn the oil and pollute the air with exhaust fumes. The burning oil is what causes more pollution. As more people grow concerned about pollution and climate change, it’s possible that 2-cycle weed eaters won’t be allowed one day because of how much pollution they release.
The 4-cycle weed eater has the advantage when it comes to fuel efficiency. More fuel being burned means less time trimming, so you will get more time out of the 4-cycle.
The 2-cycle weed eaters are typically louder than the 4-cycle. This is because its process is completed in just two strokes. The 4-cycle engines have four strokes. The third stroke, the intake stroke, closes up a cylinder inside the engine that makes it quiet. The 2-cycle engines don’t have a feature like that, so they will usually be pretty loud.
I always wear noise-canceling headphones when doing yard work with gas-powered tools. I strongly recommend hearing protection.
The 4-cycle weed eater has the advantage if you want a quieter machine. This can be beneficial if you live in the suburbs and don’t want to be disruptive to your neighbors.
Note: If noise levels and fuel efficiency are major concerns for you, it’s worth considering battery-powered string trimmers. These have come a long way in recent years. See Gas vs Electric: 6 Reasons To Use Battery-Powered Yard Tools
Okay, so just hear me out on this. A lot of people argue that 4-stroke engines are more reliable. I can agree with that. But here’s the thing…
2-cycle weed eaters have fewer parts that can break. Remember that its engine has three main parts, a crankshaft, a connecting rod, and a piston, while the 4-cycle engine has those three parts along with a camshaft, valves, and lifters. More pieces mean you have more parts that could potentially break.
And here’s the real kicker…
A 2-cycle weed eater may be easier to repair at home than a 4-cycle since it has fewer parts. There’s just less that can go wrong with it.
If a 4-cycle engine breaks and you aren’t too savvy with repairing engines, you may have to have it professionally serviced. Hiring a repairman will cost you more money, especially if you end up with a weed eater that needs multiple repairs.
Now in fairness, there is another side to this story. Two-stroke engines run at a higher RPM in general. And so, they can wear down the internal parts quicker. This means that they can break down more often, theoretically at least (source). That makes 4-strokes appealing for some.
But 4-strokes do require more ongoing routine maintenance. You have to change the oil each season, for example. That’s not something you have to worry about when it comes to two-strokes. Yes, you have to mix the oil and gas but not if you use a commercial premix like I do.
All in all, 2-cycle engines have a slight advantage when it comes to routine maintenance but 4-cycle engines have the edge in longterm durability. There are really some solid arguments on both sides for this one so maybe we call this section a toss-up.
In a perfect world, you’d make your decision solely based on your preferences. But realistically, you have to keep your budget in mind, and that’s typically the deciding factor when it comes to buying yard equipment, isn’t it?
Weed Eater Cost: 2-cycle vs 4-cycle
Basic run-of-the-mill 2-cycle weed eaters typically average between $100 and $200, but the price can go above and below this range depending on the brand and model.
4-cycle weed eaters average between $150 and $350. Again, the price will vary according to brand and model. 4-cycle engines are bigger and have more parts, so they cost more to manufacture and result in a larger price tag.
As you look at prices, be sure to research which brands are trusted and are of high quality. The cheaper weed eaters are probably going to break down more often, which means you might have to spend quite a bit of money on repairs or replacement parts. Consider that repairs will add to the long term price you invest in the equipment.
Gas and Oil Costs
Both types of weed eaters require gasoline and oil to function. 2-cycle weed eaters use less oil but 2-stroke oil is usually more expensive.
4-cycle weed eaters usually require SAE 30 oil in its own compartment. You can usually buy a quart of SAE 30 oil for about $12. You have to keep enough oil in the compartment to keep the engine lubricated, and you have to change out the oil just like you change it in your car.
You should change it after a total of 25 hours of usage. Many people just change it annually at the beginning of each season. So, the price of oil will probably end up being more expensive over time than the oil for 2-cycle weed eaters.
Which Has the Price Advantage?
This can be a little more complicated since there are several factors that go into determining the best price. Cheaper doesn’t necessarily always mean it’s a better deal. So, let’s create a summary of possible prices for each.
For the 2-cycle weed eater:
- The average price is about $150.
- Oil can be purchased for about $10.
- You won’t have to buy oil very often.
- It’s easier to repair yourself.
For the 4-cycle weed eater:
- The average price is about $200.
- Oil can be purchased for about $12.
- You will probably buy oil more frequently.
- It may be more difficult to repair yourself.
The 2-cycle weed eater has the advantage based on numbers alone. Remember that brand, model, and how much you want to spend on fuel and oil will affect how much you spend. If you want the cheapest option available, you risk sacrificing quality.
For a comparison of two of the leading brands on the market, see our comprehensive comparison: Stihl vs ECHO [Trimmer, Edger, Blower, Chainsaw, Multi-Tool]
There are two types of weed eaters: 2-cycle and 4-cycle. The difference is how the engine works. The 2-cycle engine uses one revolution to complete the cycle while the 4-cycle uses two revolutions to complete the process of creating power and bringing in air, and then release exhaust and compress the air. Since each engine completes the same process differently, they are different sizes, weights, and require different fuel methods.
The pros of the 2-cycle include:
- Requires little maintenance
- Easy to maneuver
- Requires a small amount of oil
The cons of the 2-cycle include:
- Produces more pollution
- Not fuel-efficient
- Difficult to cut through thick grass
The pros of the 4-cycle include:
- Powerful – can cut through tough grass
The cons of the 4-cycle include:
- Must spend more on oil
- Have to keep it level because of oil
Which is the best option for you? If you need a weed eater for lawn care at home, the 2-cycle weed eater might be the best option. Because it’s lightweight and easy to control, several family members will be able to use it, and it should be less strenuous, so you don’t have to wear yourself out every time you use it.
If you have tough grass to cut or care about your carbon footprint, the 4-cycle is probably better suited for you. It’s heavier and will feel like more of a workout, but it’s great for tough jobs. If you have a lawn care business, you might prefer this weed eater, especially if you want to get more use out of your fuel and use it for longer periods of time.
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