From the outdoor power equipment fuel efficiency report published by the United States Environmental Protection Agency (EPA) in 2020, it is found that the average per-hour fuel usage of the 4 stroke push mower is just 0.3-0.5 liters, i.e., roughly 40% less than the 0.6-0.8 liters of the conventional 2-stroke type. Let’s take the Honda HRX217VKA model for example. It is equipped with a 160cc four-stroke motor whose thermal efficiency is 32%. Combined with the smart throttle mechanism, it consumes only 0.8 liters of gasoline to trim a 300-square-meter lawn, while the 2-stroke unit in the same operation consumes 1.3 to 1.5 liters. This efficiency in fuel is a consequence of the four-stroke technology’s full combustion cycle design, where air-fuel ratio is kept at the theoretical best of 14.7:1, reducing the unburned hydrocarbon emissions by 72% compared to two-stroke technology (2019 California Air Resources Board test data).
From a full life cycle cost analysis perspective, the fuel efficiency advantage of 4 Stroke push mower is even more. From the United States average annual mowing of residential lawns at 30 times and each activity consuming 1.5 hours, the annual fuel cost of a four-stroke model is approximately $18 to $30, which is a reduction of $45 to $60 compared to a two-stroke model. The combined 10-year cost of use of the Toro Recycler 22-inch unit (purchase price of $399, maintenance cost of $120, and fuel cost of $270) is 38% less than the equivalent two-stroke products, and the payback period is reduced to 2.3 years. It is notable that the four-stroke engine service cycle has been extended by half, the spark plug replacement frequency has increased from 50 hours per instance in two-stroke engines to 100 hours per instance, and the oil burn has also reduced by 60%.
Market empirical evidence shows that the mass application of four-stroke technology has reduced gasoline consumption in the residential market in the United States by 120 million gallons annually (figures from the U.S. Energy Information Administration in 2021). A follow-up survey of 1,200 users by Consumer Reports found that families who used the 4 Stroke push mower saved an average of $53 per year in fuel costs and reduced carbon emissions by 142 kilograms, equivalent to the carbon sequestration effect of planting six mature oak trees. In the business community, the lawn care team of the University of California, Davis reduced the cost of yearly operation from $4,875 to $2,790 by replacing 15 two-stroke mowers with Honda four-stroke mowers, enhanced fuel economy by 41.7%, and extended the life of equipment from 5 years average to 8 years.
The technical indicator comparison shows that the 4 stroke push mower has a more obvious advantage of fuel economy in partial loading. When the engine load rate fluctuates at 30%-70%, the fuel consumption rate (BSFC) of the four-stroke system is constant at 280-320g/kWh, while the two-stroke counterpart fluctuates by ±25% under the same conditions. University of Wisconsin-Madison engineering tests show that under a simulation of real lawn resistance (cutting torque 4.5-6.2N·m), the mechanical efficiency of a four-stroke engine is 18 percentage points higher than that of a two-stroke engine because of the 16% friction loss reduction by its independent lubrication system. Such technology has made today’s four-stroke push-type lawn mowers the energy efficiency benchmark for household garden maintenance.