On July 25 the Environmental Protection Agency (EPA) published a new regulation that grants partial waivers allowing gasoline containing up to 15% ethanol (E15) into commerce for use in model year 2001 and newer light-duty vehicles.
But as of August 15, E15 had not been registered with the EPA and therefore is not yet legal for distribution or sale as a transportation fuel. It is nevertheless just a matter of time before E15 shows up at your local retailer. This should be a great cause for concern if you run off-road gasoline engines or on-road vehicles from pre-2001 model years, including outdoor power equipment such as cut-off saws, rammers, pumps, and generators.
Reason for concern
Ethanol is valued as an alternate fuel source but none of today's engines are designed to handle E15.
"Our industry and committee are not opposed to ethanol," says Kris Kiser, president and CEO of the Outdoor Power Equipment Institute (OPEI). "You can certainly design for E15, E20 or E25. The problem is the machines in the field today and the machines coming off the line are simply not designed for it."
Ethanol is a form of alcohol. "Alcohol has inherent properties that cause issues with small engines for outdoor power equipment, and these issues become more acute with increasing alcohol content," says Laura Timm, communications director at Briggs & Stratton.
Adding ethanol to gasoline changes the characteristics of the fuel. "There are four main concerns," states Michael Major, manager, engineering regulatory compliance, Kohler Engines. "First, ethanol causes fuels to degrade more quickly and is corrosive to the fuel system components (fuel tanks, gaskets, hose, carburetors, fuel injector, caps, etc.). All these components must function correctly to ensure that the engine continues to satisfy the environmental regulatory requirements and offer acceptable performance. Ethanol is a very effective detergent and can dislodge existing deposits, which subsequently obstruct fuel flow."
Second, ethanol changes the combustion chemistry. "Fueling rates should be increased to compensate for ethanol content as the optimal air/fuel ratio for ethanol is different than for gasoline," Major explains. "In engines without closed loop fuel control, the fueling rate is not adjusted to compensate for ethanol content, potentially resulting in poor startability, higher operating temperatures, higher pollutant emissions and increased engine wear."
Third, ethanol content leads to greater phase separation. "Ethanol has a greater affinity for water than gasoline and absorbs moisture from the air," notes Major. "Water displaces gasoline in the ethanol-gasoline mixture. At some concentration, the water-ethanol mixture separates from the gasoline and sinks to the bottom of the fuel tank due to its greater density. The fuel pick-ups on small engines are typically located at the bottom of the tank and are prone to draw only the ethanol-water mixture."
Fourth, ethanol has a lower energy content. "Many of these negative impacts can be overcome with proper engine calibration such as replacing carburetor jetting or remapping fuel systems. But these services are expensive and unlikely to be performed on small engines," Major points out.
Today's small engines are primarily carbureted, meaning the air/fuel ratio is fixed unless the carburetor jetting is replaced. "Unlike a fuel injection system, carbureted engines' performance, startability and emissions may degrade as few consumers are likely to have the engines properly adapted for E15 consumption," says Major.