Aircraft owners groups such as the American Bonanza Society (ABS), the (Piper) Malibu/Mirage Owners and Pilots Association (M/MOPA) and others have asked the Aircraft Owners and Pilots Association president Craig Fuller to press the FAA into action. At issue is the impending disappearance of 100-octane low-lead fuel (100LL). As the only transportation fuel still approved for any lead content, 100LL faces opposition from environmental concerns, and refiners have long faced the challenges of maintaining separate delivery infrastructure for 100LL to keep from contaminating other trucks and equipment with lead. A proposed replacement fuel would perform well in an estimated 70 percent of existing aircraft engines, but would significantly reduce the power output of higher-horsepower models that need the octane supplied by lead, such as those that power some Bonanzas, Malibu/Mirage models and others. The owners' groups have asked AOPA to pressure the FAA to approve use of the Supplemental Type Certificate process to facilitate testing of new replacement fuels. The groups would like the FAA to use STCs to permit fleet testing of a possible lead free replacement fuel, G100UL. The fuel is currently being tested in a single Cirrus SR22 registered in the Experimental category, but the groups would like to see broader testing — which would require an STC. Another possible replacement fuel, Swift Fuel, is scheduled to begin tests using the Embry-Riddle Aeronautical University trainer fleet. In resisting approval of using the STC process, the FAA has referred the groups to ASTM international for approval of the new fuels, a process that is estimated to take up to two years before fleet testing could begin.