Ethanol has become the most popular and least understood term in the lawn and garden industry.

So what is ethanol? Ethanol fuel is a biomass. This alcohol is a renewable fuel made from a number of plant materials. Typically produced from corn in the United States, ethanol has many benefits beyond being a renewable material. It reduces air pollution, oxygenates fuel, and can produce higher fuel economy in vehicles.

Ethanol is a staple of gasoline blends and sold in many different ratios. Most popular fuel blends sold in the United States include at least 10% ethanol. In early 2019, new proposals to sell E15 a fuel blend typically restricted for sale only during summer months was considered for year round sale. The future of fuels seems to be focused on increased levels of ethanol. Advanced engines in cars offer specialized features including exhaust sensors, knock sensors, and computers that tune the engine to use these fuel blends efficiently. Despite being a wildly politicized issue, ethanol has many benefits.

So why is ethanol bad for my lawnmower?

In short, ethanol is not the only culprit. Small engines are more sensitive than larger more advanced engines on modern vehicles. So we have to consider the best ways to keep them running cleanly. As gasoline and ethanol age three key problems emerge–water, temperature, and age.

Water is simple to explain. Ethanol is an alcohol and thus, by nature, it absorbs water. During humid conditions, ethanol draws water from the air into fuel containers and gas tanks. This increase in water ratio disrupts the single phase required for an engine to run. So when an engine surges or knocks, water (and ethanol by proxy) is usually to blame.

Temperature is more complex to explain. Ethanol has a lower vapor pressure than gasoline. In the most basic terms, ethanol is harder to ignite and burns hotter than lower octane gasoline. This leads to engines being hard to start during colder conditions, running hotter and breaking down faster. Small engine manufacturers typically address this issue by using improved spark plugs.

Finally, age is easy to explain. As fuel sits, water sinks below gasoline and the alcohol can separate to the top. Fuel stabilizers can help, but all sources suggest that fuel older than 30 days displays these effects. The primary reason lawnmowers and other small engines run poorly or will not start is old fuel.

In Indiana, there are very few stations that still claim ethanol free fuel ( Currently, Indiana does not require pumps to be labeled when ethanol is added ( So for local customers, there is no way to guarantee what you are buying at the pump.

Our best advice is purchasing no more than 30 days of fuel, using a no-spill container, and adding a fuel stabilizer as soon as you purchase your fuel. READ MORE

For more expert advice explore these links:

Toro Fuel Facts

Honda Fuel Related Problems

OPEI – Look Before You Pump