There are significant differences in power output and fuel efficiency between the two-stroke and 2 stroke push mower: Take the 25cc displacement model as an example. The power of the two-stroke engine can be as high as 1.2kW (about 1.6 horsepower), with a rotational speed of 9000rpm, whereas the power of the four-stroke model is usually 1.0kW (1.3 horsepower), with a rotational speed of 7500rpm. During the mowing of dense-thickness lawns (grass height 20cm, plant density 300 plants/m²), the efficiency of the two-stroke model is a maximum of 85 square meters/hour and of the four-stroke model a maximum of 90 square meters/hour. In contrast, the fuel consumption of the two-stroke model is 15% higher (0.8L/hour compared to 0.68L/hour). The carbon output is even 3.5 times as much as that of the four-stroke (HC+NOx emissions: 28g/kWh compared to 8g/kWh).
The structural simplicity is in sharp contrast to its maintenance cost: The two-stroke lawn mower has about 15 components (more than 25 for a four-stroke), and is 30% lighter in weight (6kg vs. 8.5kg). Although, it will have to mix gasoline and oil (in the ratio of 50:1), the probability of engine failure due to faulty operation is 2.3 times higher relative to that of a four-cycle engine (customer surveys suggest 73% of the two-cycle failures are caused by faulty mixture of the fuel). The four-stroke model uses straight gasoline and is approximately $30 per year to service ($45 per year for the two-stroke model), as it requires oil changes (every 50 hours) and air filters (every 100 hours) but the two-stroke model only requires an air filter change every 25 hours (for $3).
Whereas, as concerns environmental flexibility, the two-stroke model produces a more steady torque compared to the four-stroke model under sloping roads with an incline of up to 30° (12% loss in power at 85% loading compared to a loss of 15% by the four-stroke model), yet while operating in hot temperature environments (35 ° C +), the temperature of the cylinder wall goes as high as 180 ° C (maintained at below 160 ° C by the four-stroke model), leading to a 200% rise in the rate of carbon deposit for the spark plug. US EPA statistics reveal that two-stroke equipment accounts for 38% of non-road small engine emissions, prompting regions such as California to implement HC emission limits of 10g/kWh from 2023 (two-stroke engines will have to be equipped with catalytic converters to meet the standards).
Market differentiation is seen by economic comparison: Two-stroke variants are 50% more affordable ($100- $150 vs. $200- $250), and their market presence is more than 75% in developing countries (such as India and Brazil), due to the easy availability of fuel and simplicity of maintenance (mean time to repair 0.5 hours vs. 0.8 hours for four-stroke variants). But in the US and European markets, due to more stringent eco-policies, electric and four-stroke lawn mowers now dominate 66% of the market (2023 data). Particularly, 56V electric models such as EGO Power+ have captured the market with zero emissions and an electricity bill of $0.2 per hour.
The performance differences over typical situations are astounding:
Thick grass processing: The two-edge steel knife of the two-stroke type (line speed 20m/s) exhibits a rate of cut success of 90% in thick-stemmed grass (diameter 5mm), but it must be repeated twice. With the four-stroke’s stable torque (0.75N·m compared with the two-stroke’s 0.8N·m), the single-pass rate is now 95%.
Noise control is a factor of concern in that during the two-stroke mode, it is 94dB (A) that is 5dB over the EU norm. Four-stroke registers at 89dB (A) and in line with most of the world’s standards.
Service life: The average service life of the two-stroke system is 400 hours (induced by rapid wear due to high temperature), and that of the four-stroke system up to 800 hours (the system of lubricating with oil reduces friction loss).
Innovative technologies fill the gap: Honda’s four-stroke GXV50 engine, launched in 2023, has increased its power to 1.4kW (16% more than the two-stroke engine of the same class) through lightweight design (weight reduction by 20% to 6.8kg) and turbocharged combustion technology. Two-stroke producers like Husqvarna implement stratified scavenging technology to reduce emissions to 18g/kWh (still over four-stroke), and at a cost benefit ($120 compared to $220 for four-stroke). Market trends show that two-stroke engines are still expanding at a 5% per annum rate in Africa and Southeast Asia, but their market share in Europe and the United States declined from 62% in 2018 to 34% in 2023. Substitution through electrification is unavoidable.