Small-engine repair shops across the country are seeing a marked increase in the number of lawn mowers, weed eaters, chain saws and other gasoline-fed engines needing carburetor cleaning or replacement. Mechanics blame ethanol, an additive that, according to the U.S. Department of Energy, is present in about half of the gasoline pumps across the U.S.

Ethanol is a biofuel engineered from plants (usually corn). Blended with gasoline, it is sometimes referred to as “gasohol.” Ethanol, added at low levels (up to 10%) is used as an oxygenator to make gasoline burn quickly and thoroughly. Oxygenators in the U.S. gas supply were introduced in the early 1990s.

While much debate has occurred over the mandate of ethanol in the U.S. gas supply and the whole issue of whether it is a green, sustainable, economic option for the country, consumers are slowly realizing that ethanol is wreaking havoc on small engines, and some not-so-small engines.

Whether or not ethanol is a viable green option, it is prevalent in the fuel supply across the nation now. What does that mean to you? If you own any small engine equipment, a motorcycle or boat, you should know the basics about ethanol and how it affects gas-powered engines. You should also know that U.S. laws vary by state as to labeling and presence of ethanol in public gas pumps. Some states require no labeling at all for the presence of ethanol at the pumps. A few states have mandated a certain percentage of ethanol be added to all public gas pumps, with a few exceptions.

Why does it matter?

According to the EPA, E10 can be safely used in almost all cars and trucks that run on gasoline. However, there are a few car and motorcycle models whose manufacturers specify ethanol blends should not be used, even at low levels. Ethanol blends used in any model Suzuki motorcycle, for instance, will void the manufacturer’s warranty. Gasoline mixed with ethanol of a greater than 10% mixture (E10) is not recommended for small engines or marine craft. Some mechanics say that ethanol is a bad idea in any percentage for small engines.

Most small engines perform just fine with low ethanol blends, if you dutifully follow the manual for maintenance recommendations. However, if you’re not a natural at mechanics or maintaining engines, it’s easy to miss small details like changes to the gas supply, especially if it’s not labeled at the pump. If you don’t know how ethanol can affect a small engine, especially those not designed to accommodate alcohol in the mix, problems can occur. These are just a few problems owners and mechanics are seeing in small engines – many of which are not more than a year old:

-Poor engine performance; engines that stutter during operation or stall out

-Melted, brittle or deterioting rubber parts

-Rusted metal parts

-Crusty, gunky, beyond-repair carburetors

-Fuel pump damage

-Clogged fuel injectors

-Deterioration of some types of fiberglass fuel tanks

According to Kris Kiser and AllSafe (a small-engine advocate group)1, there are also safety concerns for lawn care equipment when blends higher than E10 are used in machines that aren’t meant for it. Unfortunately, gas stations sometimes sell gas with an accidental high density of ethanol in the gas, so even if the consumer thinks he’s buying E10, he’s using a much higher blend.

What Should You Do?

  • Know your state’s laws. In Missouri, labeling of any ethanol content is not required, but in 2008 the state mandated the use of 10% ethanol in all publicly-sold gasoline, with the exception of premium grades of 91 and greater. Although the Missouri mandate does not include ethanol in premium grades, gas station owners can sell premium low-level ethanol blends without labeling. Missouri does require alternative blends, like E85, to be clearly labeled.2 For more details about your state’s laws regarding ethanol, visit the U.S. Department of Energy’s Alternative Fuels & Advanced Vehicles Data Center website (found here:, and click on your state.

  • Understand the labeling lingo. “Low level blends” refer to gasoline mixed with up to 10% ethanol. In states where labeling is required there will be a small sticker on the pump with “E10” or an artistic lowercase “e” with fine print stating the maximum amount of ethanol that may be present. E85 refers to gasoline that is mixed with ethanol at a 15:85 ratio. That’s 15% gas, 85% ethanol. E85 is only recommended for flex-fuel vehicles. E15 and E20 are intermediate blends of gasoline mixed with 15% and 20% ethanol, respectively.3

  • Understand the consequences of inexact blending. “Splash blending”4 is a common and, in many states, legal method of mixing ethanol into gasoline which can result in much higher levels of ethanol than the legal maximum limit of 10%. The consequences of too much ethanol in the mix can be devastating to many types of vehicles and equipment, small or large, which are not equipped to handle gasoline blends with ethanol higher than 10%. In a car that might result in gasket failure or rust in the fuel system. In a lawn mower, it could kill the engine.

  • Report bad gas. Keep all of your gas receipts, and make a note of receipts for gas you bought to fill your small engine equipment. If you suspect fuel was to blame for problems, test the gas in the tank for levels of ethanol. A test kit costs about $25, but looking at a glass of gasoline will also work: Low level ethanol blends (E10) should be straw colored, never murky, and without any appearance of separation. Sometimes the clue can be in the number of your vehicles and gas-powered machines breaking down within a short period of time, all of which used the same source of fuel. Such was the case when a third of the Baltimore police fleet cars suffered engine trouble in a single weekend as a result of bad gas originating from a city-run gas pump.5

  • Use the correct fuel, and find a provider you trust. Using non-ethanol gas is the best solution for small engines, if it is available. In states like Missouri, where ethanol is mandated, premium grades are your best bet for equipment you don’t use regularly. Ask gas station owners where you typically buy gas about the average level of ethanol for each grade of gas. If you indicate you are looking for a provider you can trust, they may be upfront about the ethanol content in their pumps. Some states (like Texas) require owners to be honest about ethanol content when asked, but even in states without such laws, most owners are eager to win a loyal, exclusive customer.

  • Take precautions for your small engines. Follow maintenance directions faithfully in the manual provided by the manufacturer. The safest precaution is to run all of the gas out of the tank and engine until the engine shuts off from fuel starvation. The next best solution is to use a gasoline stabilizer like Stabil in the tank that sits up for prolonged periods of a week or more. Even when using non-ethanol gas, a stabilizer is recommended for machines that are not run regularly through the off season. Or take your small engine to be serviced every year by a mechanic, especially winterizing services for lawn equipment.

In the future the level of ethanol in gasoline could rise to 15 or 20 percent, which might require small engine owners to retrofit their machines for the change, or simply buy new models that can accommodate it. If the thought of doing so seems daunting, expensive and not such a great idea for the environment to you, get involved and voice your opinion to your state’s politicians.


1. “Ethanol Could Kill Your Small Engine,” by Kai Ryssdal ,

2. A checklist for purveyors of gasoline in Missouri from the Missouri Department of Agriculture and the U.S. DOE’s Alternative Fuels & Advanced Vehicles Data Center (AFDC):

3. About Ethanol blends from the U.S. Department of Energy:

4. “Splash Blending Can Put Too Much Ethanol in Your Fuel Tank,” by Steve Everly, Kansas City Star, 10-26-2008. This article can be found on the Internet here:

5. “Excess Ethanol Blames in Breakdown of Police Cars, by Justin Fenton, The Baltimore Sun, September 23, 2009:,0,1002895.story