Now that the EPA has approved the use of E15 fuel (15% ethanol) for use in cars 2001 and newer. I want to know if E15 is safe to use in my lawnmower.
No - E15 is only approved for 2001 and newer vehicles. It is not approved for use in motorcycles, heavy-duty vehicles or non-road engines. E15 will destroy your small engine. I emailed Toro, Husqvarna and Stihl for their thoughts. Stihl replied within minutes:
"STIHL only authorizes the use of fuel with up to a 10% blend of ethanol. The use of any higher will cause catastrophic damage to the engine."
I expect the same response from Toro and Husqvarna.
Apparently, adding alcohol to gasoline makes fuel more corrosive - it's my understanding that it might destroy rubber gaskets and seals.
Finally, pay attention to the signs at the pumps when fueling older cars, or other gasoline-powered machines so that you don't accidentally fill them with E15 fuel.
I only use ethanol free gas in my lawn care equipment. Even a 10% blend of ethanol can wreck an engine. Protect your engines by treating ethanol-blended gasoline with a fuel stabilizer additive. Sta-bil is my recommendation. You can purchase a whole case of Sta Bil Ethanol Treatment with Performance Improver - 10 oz., 12 Bottles from Amazon.com or from your local hardware store.
Stihl sells a canned gas/oil mix that is ethanol-free. However, Stihl's Motomix is expensive - $7.99 per quart - but that's cheaper than a carburetor rebuild...
Motomix is only available through Stihl dealers.
Update 1/26/11: Toro just replied, "We do not recommend using fuel with more than a 10% ethanol concentration."
The Mankato Free Press pubished an article on 1/24 stating: "Ethanol-blended fuel, say small engine pros, begins to break down quickly in the tank. While that doesn’t cause problems in cars and trucks, it wreaks havoc on carburetors of small engines. Consumer Reports said the unstabilized gas left sitting in engines causes them to gum up with “varnish,” as well as causing metal parts to crust up, plastic parts to stiffen and crack, and everything rubber to deteriorate."
Video: Ethanol and Your Outdoor Power Equipment. How to Prevent Issues