One-hundred octane low-lead avgas (100LL) is on its way out. Despite the fact that studies by the Environmental Protection Agency have failed to demonstrate a clearly higher risk attributable to lead emissions by piston-engine 100LL-burning aircraft, lead is poisonous in any concentration. Enormous pressure is forcing the FAA to confront this issue, and someday, one must hope, a viable replacement fuel will be available.
For general aviation, the problem is that many aircraft cannot burn anything without the detonation-prevention capabilities of 100LL. Roughly 30 percent of all piston-powered aircraft have engines that require leaded avgas. These airplanes, and probably most piston-powered helicopters, will need a replacement fuel that meets the anti-detonation requirements and can be manufactured and distributed with processes not significantly more complex than those already in place.
