The Coordinating Research Council (CRC), a nonprofit organization that studies fuel and lubricants, formed an Octane Rating Group in the early 1990s, when CRC first learned that leaded fuel would eventually disappear. That group met Tuesday afternoon at EAA AirVenture Oshkosh to review existing data and to map out a strategy for addressing the question. It's a complex problem.

To begin with, unleaded fuel needs a higher octane rating to achieve the same engine performance as leaded fuel. And the higher the octane rating, the wider the performance gap between leaded and unleaded fuels with the same octane numbers. New engine technology that features electronic controls might narrow the performance gap between leaded and unleaded fuels for some engines. But it will still be a major challenge to achieve unleaded octane ratings that will match the performance of high-octane leaded fuels in an aircraft engine in real-world operating conditions.

The Octane Rating Group aims to determine a "fleet" standard for unleaded fuel, one that will meet the needs of a broad range of aircraft engines. That goal presents some problems of its own. If you're looking for a fleet standard, which part of the fleet do you focus on? The CRC concluded that it should focus not on the largest number of engines but on those engines and aircraft that represent the highest total use of fuel-in other words, engines that operate for the highest number of hours over a given period of months or years. Using that criterion, the Octane Rating Group will focus on testing and seeking an octane standard for high-performance piston engines, the kind that pull high-use business and commercial aircraft around the sky. The group reasons that a no-lead fuel that meets the needs of high-performance engines will also be suitable for smaller, lower-performance engines.

The group will first have to test a variety of engines to determine their actual octane requirements with leaded and unleaded fuel. Then it can begin the search for a fuel specification that would provide a fleet standard for general aviation aircraft. Once that specification is determined, it will be up to petroleum companies to develop the fuels that will meet or exceed that specification.

In the end, when leaded fuel finally disappears from fuel trucks and tanks, some aircraft will require new engines, and some engines will have to be converted or retrofitted to use unleaded fuels. Some engines will be derated, producing a lower horsepower output on unleaded fuel, and some will make the transition without problems or modifications.

EAA led the way in the use of auto fuel in aircraft engines. We will continue to support and participate in research into unleaded aviation fuels, and provide our members with up-to-date information.