Lead is bad for engines and people; get rid of it!
People forget that when lead was introduced, it caused all sorts of engine problems, particularly with valves.
Now, some still somehow believe that lead is good for engines and valves.
In my personal experience, engines operated on unleaded Mogas (premium Shell) have at least 50 percent more cylinder life, do not have valve guide or valve problems, and never foul plugs.
Oil is cleaner. and oil passages do not sludge up.
Starting is easier in all weather, and some of those engines operate on fuel that may be a year old; still fine.
No Vapour lock issues, with or without fuel pumps. No problems with seals or leakages.
Octane is a separate issue, but is not a problem chemically. Octane does not require lead; that is just one way to achieve it.
What is the hold up? No one will say, except GAMI and SWIFT have fuels that work.
IF Lycoming and Continental were not scared of liability, and IF they would produce retrofittable “FADEC” ignitions and fuel injections for high compression engines, perhaps the problem would be solved, along with reduced fuel consumption.
Ford could help, or Toyota, or any engine manufacturer producing current engines with very high compression running on regular gas, let along premium. They build them by the millions; no problem.
Air cooled engines are more difficult than liquid cooled, but even there, the compression ratios are relatively low compared to modern engines.
It seems there is no will to solve the problem, and perhaps that the FAA doesn’t even understand the problem.