Ethanol Problems

Engines produced to date for use in outdoor power equipment are not designed for gasoline with ethanol (such as E10, E15, E20 and E85); using higher ethanol fuel blends may lead to engine damage and/or performance issues.

During periods of extended storage, ethanol tends to draw in atmospheric moisture which can lead to a build-up of water in the carburetor bowl and fuel tank. Since the carburetor is vented and the moisture in the air is being taken up by the ethanol, new air brings more moisture through to the vent. Inside the carburetor bowl, because the density of water is greater than gasoline, the ethanol/water mixture separates from the gasoline and settles to the bottom of the bowl.

Industry refers to this as “Phase Separation” and because the fuel pick-up inside the carburetor bowl is located on the bottom, the first thing sucked up through the jets is the ethanol/water mixture. The water sent to the engine causes poor performance, higher engine temperatures and engine vital parts damage. The ethanol / water mixture at the bottom of the carburetor bowl causes carburetor internal parts corrosion.

On the other hand, the ethanol and water mix in gasoline is a breeding ground for microbes like bacteria and fungi which just adds to the corrosion and debris inside the carburetor bowl. These deposits clog the carburetor jets and fuel and air passages inside the carburetor which is main reason why the engine won’t start or operate poorly.

Even if the engine is run dry at the end of the season, there will still be some fuel left in the carburetor. This turns to gum and varnish and dirt and restricts the passages inside the carburetor.

It is impossible to empty all of the fuel from any engine system so there is always old fuel somewhere in the fuel system and inside the carburetor.


Most engine manufacturers recommend using a fuel stabilizer or draining the fuel system before putting the machine into storage.

Most fuel stabilizers form a layer over the top of the gasoline and reduce the rate the fuel's volatile compounds evaporate. They also prevent the absorption of moisture by the fuel.

Fuel stabilizer will not prevent but will only retard the separation into more than one phase of gasoline-ethanol solutions in the presence of small amounts of water.

US Department of Energy’s Oak Ridge National Laboratory warns against the use of ethanol with zinc or aluminum carburetors. Additives designed to help prevent phase separation generally contain alcohol which can make the corrosion problem worse.