Two-stroke engines and the environment

- By Patricia Hanbidge

September 26, 2025

key points from this story:

• One hour leaf blower matches truck pollution.
• Many lawn tools use two-stroke engines.
• Two-strokes pollute due to engine design.
• Oil mixed with fuel increases emissions.
• Pollution affects air and water quality.
• Electrics offer cleaner equipment options.

The other day, my attention was riveted by what was on the radio. A repeat of a What on Earth show was airing and what caught my attention was that they stated that one hour of use of a gas-powered leaf blower released the same amount of emissions as driving a “big truck” from Saskatoon to Vancouver following the longest route (1750 km). I have traveled that road many times. Usually, I now take three days to make that journey and the thought of using a gas-powered leaf blower for an hour having the same emissions was rather horrifying.

The show was a bit alarming, so I thought I should dive deep into what was being shared. It is true that many lawnmowers, gas-powered leaf blowers, dirt bikes and small outboard motors are generally two-stroke engines. This means they are a type of internal combustion engine that completes its power cycle with two movements of the piston (up and down), resulting in a power stroke for every crankshaft revolution. This is the engine of choice because it is simpler, lighter and has a high power-to-weight ratio. This power is extremely important if you make your living doing landscape maintenance as you can ultimately achieve more in less time. However, these two-stroke engine tools are less fuel-efficient, noisy and produce more pollution than four-stroke engines.

The reasons that two-stroke engines significantly pollute the environment is because of their design and the lubricant-fuel mixture. The intake and the exhaust ports on a two-stroke engine open simultaneously, so some of the fresh fuel-air mixture can escape through the exhaust. Because they use a lubricating oil along with fuel in a two-stroke engine, some of it is burned and emitted with the exhaust gases which contributes to the smoke, oily residues and that familiar smell. The fresh fuel-air mixture that is exhausted results in higher levels of volatile organic compounds (VOC’s), like benzene and polycyclic aromatic hydrocarbons (PAH’s). The combination of unburned fuel and burning lubricating oil results in higher emissions of hydrocarbons, other pollutants and substantial amounts of fine particles, which are harmful to respiratory health.

As we can now understand a bit more about two-stroke engines, there is a significant increase in environmental impact affecting air quality. The oily residue can make it into our waterways which affects the aquatic ecosystem and there is some evidence that water polluted by two-stroke engines remains more toxic for a longer period of time. Some cities and regions that have strict air and water quality standards have banned the use of two-stroke engines due to the severe environmental impact. It is important to note that modern two-stroke engines with direct fuel injection are significantly cleaner than the older models. Over the years I have had a love-hate relationship with two-stroke engines and in particular gas-powered leaf blowers, small outboard motors and other equipment commonly used in the landscape maintenance industry. They are noisy, they smell and I often find them difficult to start. However, in many cases due to their high power-to-weight characteristics, they really do reduce the workload if the operator is experienced. I admit, I have a Stihl gas-powered leaf blower. It has served me well for many years, but I do rake up and take away the debris I blow around to minimize the use of the blower. I am thankful that there now are many more choices that consumers can exercise in choosing equipment that traditionally only existed in the older models of two-stroke engines. My new purchases of landscape equipment are electric if possible. This means an easy start every time I use the machine, quieter operation and most importantly an emission-free operation.