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.