2 Cycle vs 4 Cycle Trimmer: Which Is Better?

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Choosing what kind of trimmer to add to your lawn care arsenal isn’t an easy decision to make. Learn about two and four-cycle trimmers, including their similarities, differences, and major differentiating factor. We’ll teach you when to use a two-cycle trimmer, when to use a four-cycle trimmer, and which is better overall.

What Is a Trimmer?

A trimmer is a lawn care device. They are informally known as weed eaters, weed whackers, or string trimmers.

A man using 2 cycle trimmer on grass

Trimmers have electric or gas engines, encased in plastic housing near the handle of the device. A pole or rod extends several feet from the engine housing. At the opposite end of this rod is a thin string, made from monofilament line.

The power of the engine turns a spindle, which whips the monofilament line around in a circle. When introduced to grass, small weeds, or other low foliage, the monofilament line takes the place of a blade, cutting plants down to size.

A trimmer is often used in combination with a good lawnmower. The lawnmower excels at cutting grass in large, open, flat spaces. The trimmer takes care of edges, tight corners, borders, and uneven ground.

There are two types of gas-engine powered trimmers available for purchase. They are differentiated by the way their engines work. Each kind of trimmer engine has its own cycle.

What is an Engine Cycle?

Internal combustion engines produce power and turn crankshafts by converting fuel into energy. There are four parts to this process. The process repeats over and over again, as long as the engine is running. Each repetition is known as a ‘cycle’.

In a single cycle, the following four steps must happen:

  • Fuel and air enters the cylinder
  • The fuel and air is compressed by the piston
  • An explosion happens, converting fuel to energy
  • Exhaust exits the cylinder

What Is a 2 Cycle Trimmer?

Two-cycle is a shortened version of the phrase ‘two-stroke cycle’. A two-cycle trimmer is sometimes called a two-stroke trimmer. Each stroke refers to the up or down movement of the piston.

In a two-stroke cycle engine, the first three steps in the process happen in a single upward motion of the piston. New fuel and air are drawn into the chamber, the mixture is compressed and ignited. After the explosion, the piston moves back down into the cylinder, allowing the exhaust to exit.

Two-cycle trimmers have three moving parts: a crankshaft, a piston, and a rod that connects the two.

A woman cutting grass using a trimmer

What Is a 4 Cycle Trimmer?

A four-stroke cycle trimmer has a combustion engine with a piston that moves four times in each cycle. Stroke, in this context, refers to each movement of the piston.

In a four-stroke trimmer, each part of the engine cycle happens independently.

  • On the first stroke, the piston moves up, creating room in the cylinder. A blend of fuel and air enters the piston.
  • The second stroke sees the piston move downward, compressing the fuel and air to prepare for ignition.
  • The third stroke happens as a spark ignites the fuel/air mixture and the piston explodes upwards.
  • As the piston moves back down on the fourth stroke, it pushes the exhaust out of the cylinder. This completes the cycle.

Four-stroke cycle trimmer engines have a lot of moving parts. The crankshaft, piston, and connecting rod all move together. A four-stroke cycle trimmer engine also has lifters, valves, and a camshaft.

2 Cycle vs 4 Cycle Trimmer

Compare and contrast the two-cycle and four-cycle trimmers to determine which one best meets your lawn care needs.

Similarities

Two-cycle and four-cycle trimmers have the same purpose and the same power source.

Purpose

Both two-cycle and four-cycle trimmers are built to achieve the same purpose: clearing grass, weeds, and other plants from areas that are uneven or otherwise difficult to access with a mower.

Power Source

Both two-stroke and four-stroke trimmers are powered by gas-fueled combustion engines.

Differences

The differences between two and four-stroke trimmers include the costs to purchase and run these machines, how much they weigh and the amount of noise and pollution they produce. The consistency of cutting power is another difference between them, and they are fueled in different ways.

Purchase Cost

Two-stroke trimmers are less expensive than four-stroke models. Two-stroke cycle engine trimmers start at around $100 and seldom cost more than $200. A four-stroke cycle engine trimmer is likely to cost at least $150, and more expensive models sell for close to $400.

Running Costs

A four-stroke engine intakes fuel only once per cycle. Fuel flows into a two-stroke engine every time the piston moves, and some of that fuel is wasted.  A four-stroke engine, therefore, uses fuel more efficiently than a two-stroke engine.

More efficient fuel usage works out to lower fuel costs, decreasing the total running cost of your gas-powered trimmer.

Weight

Two-stroke cycle trimmers have fewer parts than four-stroke cycle trimmers, so they weigh less. This makes a two-stroke trimmer easier to hold and operate for long periods of time.

Emissions

Four-stroke trimmers emit less pollution into the environment. Some municipalities have outlawed the use of two-stroke trimmers for this reason.

Noise

Four-stroke engines run more quietly than two-stroke engines, so a four-stroke trimmer will be quieter than a two-stroke trimmer.

Consistent Cutting Power

A two-stroke trimmer operates at a higher speed than a four-stroke, spinning the trimmer line in more rotations per minute (RPM). Encountering thick weeds or difficult foliage, the speed will slow, reducing the cutting power and cutting speed.

Four-stroke trimmers spin fewer times per minute, but produce more torque, or rotational force, than two-stroke trimmers. This power is more consistent even at lower speeds, allowing four-stroke trimmers to chew through the toughest material.

Combined with the best trimmer line on the market, both two stroke and four stroke trimmers can make short work of dense weeds.

Fuel Requirements

A four-stroke trimmer has two tanks; one for fuel, and another for oil. The machine will only stay lubricated in certain positions, due to the way the oil is routed through the engine.

Two-stroke trimmers have only one tank. Fuel and oil must be mixed in an appropriate ratio in order to power the machine. However, two-stroke engines enjoy more consistent lubrication in more positions.

Fuel Intake and Ejection

A four-stroke cycle engine has valves that open and close, allowing air and fuel to enter the cylinder and emitting exhaust. A two-stroke cycle engine does not have valves. Instead, ports allow air and fuel to flow into the cylinder depending on the position of the piston.

Ease of Repair

Because two-stroke cycle trimmers have fewer moving parts than four-stroke cycle trimmers, they are easier to troubleshoot and repair when things go wrong. A four-stroke cycle engine will likely require professional maintenance if something breaks, while a two-stroke cycle engine can often be repaired by the consumer.

Major Differentiating Factor

The major differentiating factor between these two products is how much maintenance they require.

A four-stroke cycle engine has many more moving parts than a two-stroke cycle engine. More moving parts equals more opportunities for things to go wrong.

Because the fuel and oil are added separately in a four-cycle trimmer, the machine must be kept upright to remain properly lubricated. In a two-stroke cycle trimmer, the lubrication is mixed in with the fuel, allowing the machine to be stored and used in any position.

In addition, you must change the oil in a four-stroke cycle trimmer after every 25 hours of usage.

When to Use a 2 Cycle Trimmer

Use a two-stroke cycle trimmer when you want a lower-cost, lightweight tool that is easy to use and maintain.

Before purchasing a two-stroke cycle trimmer, make sure there are no regulations governing the use of trimmers in your locality. Some areas have banned two-stroke cycle engine-powered tools due to the noise and pollution they produce.

When to Use a 4 Cycle Trimmer

Use a four-cycle trimmer when you are ready to invest in a robust machine that will last a long time.

If you choose a four-cycle trimmer, be prepared to change the oil periodically. You may want to have a small engine mechanic in mind should anything go wrong.

Depending on your municipality or homeowner’s association, a four-cycle trimmer may be your only option, as some localities have outlawed the use of noisier, emissions-heavy two-cycle trimmers.

Which Is Better: 2 Cycle or 4 Cycle Trimmer?

A four-cycle, or four-stroke trimmer, is better than a two-cycle or two-stroke trimmer in almost every way.

Four-stroke trimmers maintain consistent cutting power, while two-stroke trimmers can lose power when confronted with tough weeds. A four-stroke trimmer is quieter than a two-stroke trimmer, emits less pollution, and uses fuel more efficiently.

Four-stroke trimmers tend to last longer than two-stroke trimmers, and you do not need to mix your own fuel/oil blend in order to use them.

A four-stroke trimmers is also more expensive than two-stroke trimmers, but the quality and longevity of these machines make the price tag worth it.

It would be a good idea to try out both a two-cycle and four-cycle trimmer before making your final selection. Some find that the noise and vibration of two-cycle trimmers make them unpleasant to use, while others find a four-cycle trimmer to be too heavy and cumbersome for effective use.

Ellenkate grew up on job sites run by her family’s construction company. She earned her theater degree from The Hartt School, a prestigious performing arts conservatory in Connecticut. Her design and DIY work from her Chicago loft was featured in the Chicago Reader and on Apartment Therapy.