There is an old adage that success has hundreds of parents, but failure is an orphan.
We see that when we look at the history of leaded fuels.
When I started at Shell Oil in 1967, my first project was to optimize the lead and scavenger levels in auto fuels. I started by reading most of the technical reports in the company library.
I was surprised to find that there was a long list of metals that worked as anti-knock additives. Apparently, the metal additives all retarded the pre-flame reaction that occurs just prior to the actual combustion flame in the cylinder.
The reports covered work at Shell and throughout the industry. There was research from many different labs that covered solubility, anti-knock performance, negative side effects, necessary scavengers, and on and on.
The compromised solution was tetraethyl lead (TEL).
TEL was used in almost all auto fuels and avgas because it raises the octane of fuels at a fraction of the cost incurred by increasing the severity of the refining process.
During the 1930s, there was a very large effort by the industry to develop 100/130 avgas. Again, no one person or company was the sole inventor. The formula for 100/130 was set by the government and any oil company could produce it if it had the necessary equipment and facilities.
Then in 1947, ASTM adopted the D-910 specification, which defines the 100/130 formula, as well as 80/87 and 115/145 grades of aviation gasoline. This remains in effect with minor changes, such as the addition of 100/130 low lead in the early 1970s.
That is a brief history of how we got to where we are now. The big question is where do we go from here?
For more than 25 years the industry has been looking for an unleaded 100/130 octane fuel to replace 100LL. But this search is very different from the search in the 1920s and 1930s.
In those searches it was a very large cooperative effort to find an answer — and they were looking for one candidate that could be produced by everyone.
But today in our search for a 100 unleaded avgas, we have two, maybe three candidates, non-standardized specification, and a host of problems and unresolved issues.
So Many Questions
If there are three different standards, would a pilot have to have three STCs or find a fuel qualified against three separate specifications?
Are the fuels compatible with each other?
Do any of the fuels provide protection against exhaust valve recession?
What about seal and fuel system component compatibility with each fuel for every aircraft and fuel system?
Will the fuel cause abnormal and harmful engine deposits?
Will some states not allow the fuel because of ground water contaminates?
The list goes on and on, including a big one: Since no major oil company has a candidate, who will be able to supply an unleaded avgas to all parts of the country — actually all over the world?
I know there are some negative concerns with big oil companies, but they are needed for technical support, adequate supply, and distribution sites to ensure continued and on spec fuel to everyone.
I also know that lead can cause spark plug fouling and some deposits in the cylinders.
But these are problems we know about and, I believe, are better than any of the new problems that may surprise pilots at the most inopportune times — like at 8,000 feet.
