Huh. I had no idea leaded fuel was still a thing in aviation.
Even in countries like the UK which offered limited exemptions for "classic" cars, the fuel companies don't care, selling a few thousand litres per year of this weird special fuel makes no sense at their scale, so even with a regulation allowing this, it quickly died out. It was (maybe even still is?) legal to buy leaded gasoline ("petrol") in the UK for a really old car, but that's useless because nobody will sell it to you, it's just not profitable at the incredibly low volumes. Classic owners who run with leaded fuel these days buy their own additives and mix it at home, but also these cars are getting fragile, they probably belong in a museum anyway, not clocking up miles driving around, and in a museum display they don't need fuel.
However if an aircraft engine dies, even though pilots of single engine piston aircraft are trained to assume that will happen in any phase of flight (because it can) that's extremely dangerous, complete engine failure over mountainous terrain could mean that your best case scenario becomes trying to land your plane (well, now glider) in some untried clearing and if you survive then maybe needing to walk out because in some cases nobody is looking for you. So engine failures translate into fatalities at a significant rate.
Planes are very expensive, and so they have long lives, which means many aeroplanes built long before leaded fuel was prohibited are still flying.
On the other hand, notice this is about piston planes. So, you're mostly talking about smaller planes for personal use, and maybe some agricultural or business purposes but less often. For scheduled aviation, you're never going to be on a piston plane. To a layman it's less obvious because although they don't have piston engines lots of smaller or shorter range planes have propellers like an old-timey plane. But their propeller is driven by a jet engine, and that runs on JetA - kerosene fuel not leaded gasoline: https://en.wikipedia.org/wiki/Turboprop
I won't miss those.
I won't miss the lead either.
Plenty of 100+ octane unleaded fuels out there.
Like, Mazda is running 14:1 compression ratios in gasoline engines, but 7:1 is considered normal for a naturally aspirated Lycoming and it'll often dip into the 6's for turbocharged versions.
Cessna has the best selling model of airplane of all time, the 172, which has sold around 45K units since its introduction in 1956.
Mazda sells that many cars in a typical 2 month period. It’s no surprise that there’s more non-recurring engineering investment in car engines than airplane engines.
There have been tons of advances in general aviation, look at panel technology between now and 15 years ago. That's awesome! Let's do the same thing but for engines now. But it isn't going to happen as long as no one is pushing for it; we have the efficiency in automobiles we do now because regulators have been pushing for better fuel consumption and lower emissions for decades. It'd be great if there was similar pressure applied to aviation.
I'd love to have a 172 that had no mixture knob and no issues with hot starts. Man, wouldn't that be awesome? This is what we should be asking for, not apologizing for why we're stuck with mechanical FI, carb heat, and shock cooling worries.
If Lycoming or Continental spend $25M on a new engine program and sell them for 15 years in all 172s, it’s around $22K per airplane or around 550 basis points. When investments in engine development are over 180x more expensive on a percent of sales basis and over 2000x as expensive on a per-unit basis, it’s unsurprising that few companies are stepping up to do that development.
I don’t mind at all if you want to lobby for it; I think there are improvements that could be made, but I think you’ll find the economics daunting and the current engine tech to be pretty well matched to the application.
_Certifying_ them is hilariously expensive for the manufacturers and users.
One can certainly fix that, but that's how it is. Main reason why the planes that consume automotive gas the most are in the 'experimental' category.