Ethanol and Your Lawn Mower

Gasoline that includes more than 10 percent ethanol can damage your lawn mower engine, carburetor, and fuel system. (Courtesy: Emilas Lex)

Gasoline that includes more than 10 percent ethanol can damage your lawn mower engine, carburetor, and fuel system.
(Courtesy: Emilas Lex)

If you own a car or a lawn mower in the United States, then you have visited your neighborhood gas station more than once. You’ve probably noticed that the gas that is going into your car has a blend of either 10 percent (E10) or 15 percent (E15) of ethanol.

The United States government has mandated the use of ethanol with gasoline to reduce the use and cost of gasoline.

No doubt you obtain gasoline from the same stations at which you fill the tank of your car. Although ethanol doesn’t appear to have an adverse affect on automobile engines, it can cause problems in your lawn mower.

Most lawn mower manufacturers seem to be okay with the use of gasoline that has been blended with 10 percent ethanol. However, there seems to be an issue with blends that use 15 percent ethanol.

The Outdoor Power Equipment Institute (OPEI) suggests that you don’t use a gasoline mixture marked as E15 in your lawn mower because the substance can be corrosive and can seriously damage fuel systems that are not designed to handle it. E15 fuels burn significantly hotter than the E10 or ethanol-free gasoline. This can cause a lawn mower engine to overheat. Moreover, ethanol blends can absorb water from the atmosphere and, under humid or damp conditions, can make a lawn mower engine difficult to start and make it difficult for the carburetor to ignite the mixture on cold days. Keep in mind that most lawn mower gas tanks and carburetors are vented and this gives ethanol the opportunity to absorb water from the atmosphere.

Ethanol can also cause your lawn mower to stall. That’s because it absorbs the moisture and gums up fuel systems of small two-stroke motors.

Keep in mind that the shelf life of gasoline with ethanol is about one month while ethanol-free gasoline has a shelf life of about three months.

Some say that ethanol can damage the carburetor causing the need to replace it. The alcohol content of the ethanol can devour rubber hoses and clog the carburetor.

Lawn mower manufacturer Toro suggests that you use ethanol-free gasoline. The company also recommends that you use unleaded gasoline with an octane rating of at least 87.

Toro warns that if you use unapproved gasoline in your lawnmower and the fuel system, carburetor and/or engine is damaged, you may not be covered by the warranty.

Toro points out that you can use biodiesel in its diesel-engine mowers. The company notes that environmental benefits of biodiesel include lower greenhouse gas and soot emissions than petroleum diesel fuel. In addition, it is cleaner burning and biodegradable and nontoxic.

Therefore, you should take precautions when seeking out gasoline to fuel your lawn mower. Use a gas station that offers ethanol-free or E10 gasoline. If you have a diesel-engine lawn mower, then check to see if the station offers biodiesel fuel. All fuel pumps include a label that details if the gasoline being pumped is an ethanol blend, ethanol-free gasoline, diesel, or biodiesel. Never purchase gasoline that has more than 10 percent ethanol. If you reside in a state that mandates ethanol blends, seek out what is called “non-oxygenated” fuel. This type of fuel is not easily available, however, it is approved for use in outdoor power equipment, motorcycles, off-road vehicles, boats, and other recreational vehicles.

About Robert Janis

Written by Robert Janis for LawnEq - Your specialists for Lawn Mower Parts and Small Engine Parts. We offer genuine premium OEM parts for Land Pride, Toro and many more dependable manufacturers.

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