The Outdoor Power Equipment Institute (OPEI) made its position clear on this issue during recent testimony in front of the House oversight committee on environment and public works. At STIHL our basic recommendation is that fuel be as high an octane rating as possible, at least 89, and contain no more than 10% ethanol. STIHL customers should also be aware that using fuel containing more than 10% ethanol could void the product warranty.
(broken link removed to http://stihlusa.blogspot.com/2011/05/stihl-motomix-offers-convenience-and.html)
(broken link removed to http://stihlusa.blogspot.com/2011/05/stihl-motomix-offers-convenience-and.html)