I enjoy AVWeb on YT for AV news (really, I just enjoy the humor/personality of Paul Bertorelli lol), here are a few insightful videos that summarize the story:

The Long, Twisted And Slightly Ridiculous Story of Avgas Part 1 (14:22) https://www.youtube.com/watch?v=9F-WngVMJBQ

Part 2 (15:15) https://www.youtube.com/watch?v=Mvse4Xhzwuk

and

G100UL Approved Now What? (When the FAA approved the first unleaded 100-octane avgas a year ago) https://www.youtube.com/watch?v=ibIkuyBL9i8

It's not odd, it's exactly what you'd expect. The only odd thing is that it took this long.

Many (older) aircraft engines need leaded fuel.

I’ve actually never experienced the, “California gas sucks” issue that car people from the mid-west talk about, have never had an issue with it. ¯\_(ツ)_/¯

Not that it matters when everything made for "premium" is tuned for 91 from the factory anyway, not 93

1) Few refineries make it, so it's MUCH more expensive. But if you're living in California, it is easy to miss because EVERYTHING is much more expensive.

2) Mileage is generally poorer, due to the mandatory ethanol mixes. But some places also usually mix in ethanol, and the difference is usually in the 10-15% range. So unless you have a good A/B comparison going, it's also easy for it to blend in with all the stop and go driving, and terrible road conditions.

3) Mandatory Ethanol means generally very poor storage characteristics. Which considering how much driving happens in California (and how dry the climate is in the populated areas), most people won't notice.

So does it suck? Comparatively, definitely! Is it likely to be noticed unless you're very aware and have experience with other options? Nope.

In the case of my vehicle it results in low/rough idle and positive fuel tank pressure which otherwise do not occur either at lower elevation or with ethanol-free fuel at elevation.

No idea about 240z specifically, but at least things designed for sustained high performance (like aero engines) tend to use valve seats made from some wear and temperature resistant alloy like stellite or brightray.

The recently developed G100UL unleaded fuel requires a change to the type certificate of the airplane (by serial number) and engine(s) (by serial number) to be legal.

Until that supplemental type certificate existed, these airplanes did legally need leaded fuel.

> Once it's legal

exception above.

If you can run, 100LL, you can run G100UL. The main issue is with mogas (standard car gas) - many aviation engines can't run it.

Another aspect is that many piston airplane engines need high octane because they have relatively high compression ratios: WWII era engines need 130 octane to develop full horsepower (they can be operated at reduced manifold pressure on currently available 100 low-lead gas), and even many post-war civilian engines require 100 octane.

Still another aspect is that the FAA is relatively conservative and doesn't want to approve something that might lead to, for example, vapor lock or fuel freezing issues.

I mean, high octane and compression relative to other 1960s engines. The common engines in nearly any single prop cessna have about a 9:1 compression ratio, which was massive back when it was built, but laughably bad compared to anything manufactured after the advent of Fuel injection and better piston geometry.

Modern cars regularly have over 12-1 compression ratios on 87 octane.

1960s era carbs and top ends were just abysmal and did a terrible job of mixing the fuel and air charge and controlling the flame front, because we just didn't have the kinds of computer controls and fluid dynamic simulations we have now, to dynamically prevent knock.

Rotax engines are modern and can reach identical performance figures or better, with the same weight or lighter, simply by using modern techniques like fuel injection or a small turbocharger. They do this while running on 91 octane

In the mean time, rebuilds have to meet the existing design. Which has specific standards.

It's not like Cessnas themselves can't be wildly improved on in general!

As an old Boeing engineer friend of mine used to say 'when the weight of the paperwork exceeds the gross weight of the plane, it will fly.'.

2) Lack of solid quality control relative to aviation fuels (see #1)

3) Power to weight ratio matters a LOT in aviation, and aviation engines run at typically far higher elevations for at least part of their flight time. So aircraft engines generally push things harder, have higher compression, and can be damaged more easily with 'junk' or contaminants.

[0]: https://www.bloomberg.com/news/newsletters/2023-10-12/fake-p...

[1]: https://www.bloomberg.com/news/features/2023-10-11/fake-part...

Same thing with running certain large piston airplane engines on 100. They blow up.

> There are several options that involve no lead, generally substituting with ethanol

Ethanol is corrosive to aluminum. Thankfully airplane designers have never used aluminum in airplanes...

You still have to apply for and buy an STC for your specific airframe's serial number and engine's serial number. Then you have to add some paperwork to the logbook and POH and add placards to the fuel fillers and cockpit.

In theory you should be able to automatically get it for anything which was approved from the factory to use 100LL, but the STC application form (here: https://stc.g100ul.com/aircraft/) does not allow you to select most mid-century large radials (which were usually originally certified on 130) or the airplanes they were installed on.

To be clear, this is a great thing, but you can't legally just fill G100UL in any random airplane.

I don't think it needs to work in every conceivable 100LL aircraft: just almost all. Every is a high bar.

Airports don’t always have the space for a second avgas tank (if this is the in between option), and if they did don’t necessarily want to spend money on setting up that infrastructure. So the current catch-all is to provide leaded which is cheaper and guaranteed to work in everything.

I think it’s great we are getting this forced through - it will make the approval process streamlined (like loda was) and removes a major reason people used to push airport shutdowns.

Lots of airports are owned or regulated by local governments which might want to move that single tank to just unleaded. E.g. Santa Clara County banned 100LL at local airports.

Forklift upgrades suck, too. You're best off getting some of the way along and then forklift. Arguably we're reaching that point.

The TC says you must run 100LL. The STC says you can freely mix G100UL in any ratio. The legal/certification problem is solved.

I'll be doing it, as soon as our home base carries it for my 56 o200.

"Regulations are the only way to solve market externalities" is not the same statement as "All regulations solve market externalities".

The market can never solve market externalities, by definition.

While this is often true, that doesn't mean it's actually an improvement.

>Will I have to modify my engine or aircraft to use G100UL avgas?

>Other than placards, no modifications are required. A small placard is attached to the engine and "stick-on" placards are applied to refueling ports. In addition, there is a short POH supplement added to the AFMS.

Anyone commercial already has to go in for 100hr inspections all the damn time. The STC is unlikely to cost much relative to that, nor to add much additional hassle.

Anyone private can deal with it, they own their own plane and knew it wasn’t going to be a cheap hobby going in.

G100UL will cost a bit more than 100LL but it seems likely this will change a bit as it becomes more widely used.

I guess it puts people operating midcentury radials that haven’t yet been certified for G100UL in a weird spot.

Operating a plane is a privilege, not a right.

Oh, we aren't talking about tire dust? Never mind.

Unlike lead, we've only recently had the technology to measure and quantify tire wear pollution. For example, we didn't realize until 2020 that 6PPD - already toxic to many aquatic organisms - can oxidize become 6PPD-quinone, which is acutely toxic to coho salmon and some other fish species. This solved a 20 year old mystery of so many coho salmon died after a rain storm.

That's why the California Environmental Protection Agency has passed a rule requiring tire makers to declare an alternative by 2024. https://dtsc.ca.gov/scp/motor_vehicle_tires_containing_6ppd/

That's in addition to the particulate pollution from tire wear. ("Research from Emissions Analytics shows that particulate mass emissions from tire wear is thousands of times greater than those from tailpipes, which have been vastly reduced in recent years by high-efficiency exhaust filters." - https://edition.cnn.com/2022/08/16/world/tyre-collective-mic... ).

We of course need to regulate them better because electric cars are heavier, so tire particulate pollution is expected to increase over the next few years.

There's also brake pad pollution, like the EPA's Copper-Free Brake Initiative to remove copper, "mercury, lead, cadmium, asbestiform fibers, and chromium-six salts in motor vehicle brake pads." https://www.epa.gov/npdes/copper-free-brake-initiative . That's a voluntary program, but California and Washington have mandatory requirements.

I trust that you support these efforts to reduce car pollution, and are not simply using the lack of discussion about them in this thread in order to score internet points for implied hypocrisy?

Both tires and brakes have the advantage that they are replaced every few years/decade, so regulations can target manufacturers. An aircraft engine can have decades of life, so any costs of switching away from leaded fuel are felt directly by the owner.

They’ve also been known as a class as a problem (along with catalytic converter particles) for well over 30 years.

There have been multiple studies linking proximity to freeways with asthma and decreased life span, serious health issues like COPD, and even significant increases in sudden unexplained deaths.

45 million Americans live within the high risk zones (300 feet or meters, I forget), countless new daycares, old folks homes, and residential high rises get built there every day, and almost every American is exposed significantly due to being in vehicles on average of an hour a day with insufficient filtering.

[https://www.epa.gov/sites/default/files/2015-11/documents/42...]

The issue here isn’t that aircraft engines last ‘decades’.

It’s that aircraft owners are only legally allowed to use fuels approved by the FAA for their aircraft, and per the various authorizations for their aircraft. Which vary. The engines may get rebuilt, but without a very expensive type change and approval (often from the manufacturer) they’re the same design as the original. Which has the same limitations.

So until there is a viable authorized replacement (per the FAA), literally they can’t use it except in emergencies. Which only just became available. And they can’t change engines either. And they can’t just YOLO it legally.

Because fuel is a major cause of crashes that kill people already (usually contamination, or wrong fuel causing engine failures/flameouts).

And despite the FAA knowing of the risks of lead (or more precisely, knowing the various factors), they only recently did authorize a replacement.

So it’s as if that study on those plastics happened 30 years ago, and we’re just now getting around to it. Which essentially is what has happened with cars and the various pollution.

So raking anyone over the coals when a far larger, more damaging, and widespread crisis has always been going on for even longer and gets ignored? Yeah I’m pointing out the hypocrisy.

It’s always about resources in proportion to risk, and arguably the FAA has dumped far more resources and mitigated a far less damaging risk (in many concrete ways) far faster with this leaded fuel issue than one near and dear all of us.

Which also drives the call to reduce car use, wherein someone is also likely to point out that driving is not a right but a privilege.

> So it’s as if that study on those plastics happened 30 years ago, and we’re just now getting around to it. Which essentially is what has happened with cars and the various pollution.

Yes. And lead wasn't banned for interior paint until decades after some other countries. The US regulatory system is strongly weighted in favor of business over health and environment.

> raking anyone over the coals

As if! This is finding. The EPA must then "propose and promulgate emission standards", which the FAA must then turn into regulations.

It sets no deadlines, it makes no policy changes other than for the EPA and FAA.

I suspect it will take years before the first regulations appear, and with years to allow a changeover.

Like small planes are spewing lead over everywhere they’re flying. I’m glad this is happening.

I don’t really care about small operators vs the health of everyone else, and especially kids in the case of lead.

AVWeb did a couple videos on the subject here:

https://youtu.be/9F-WngVMJBQ?si=Qb_IYu4QwZlOTDCv

https://youtu.be/ovJBJjZTjsk?si=f2OwwZMmuEUTx6wL

More specifically, I believe they certified that a particular fuel as suitable for use in ALL engines that previously relied on leaded fuel. Until that happened there was a somewhat legit concern about banning leaded fuel. What people are afraid of now is a monopoly on the new fuel leading to higher prices. But there's already a near monopoly on leaded avgas.

It would be really cool if someone developed a new aircraft engine suitable for replacing all the old models and able to run on a wide range of fuels (this may actually exist). But even then its a slog to get that engine certified for all the planes you'd want to use it on.

If you can afford private aviation, the price of the fuel is not going to be a big concern. It's already $7-10/gallon and that is a pretty small component in the all-in hourly costs of operating an aircraft.

As a recent article here talked about, nobody is making new aircraft for general aviation. Or at least, nobody is making anything innovative for it.

But there exist plenty of engines that are good enough for planes and can run on a wide range of fuels. They are just not getting into GA planes.

Except that they did approve a lead-free fuel for use in all those engines last year. Banning leaded fuel is the obvious next step.

I have never flown to an airport with it yet. i have probably landed in over a dozen different airports in the last few months with a leaded gas engined plane.

What is $250 in aviation terms? It's nothing.

Availability of fuel is a concern, sure. But a fire has to be lit on people's ass, otherwise they will not move.

> The FAA signed on September 1 supplemental type certificates that allow General Aviation Modifications Inc.’s 100-octane unleaded fuel (G100UL) to be used in every general aviation spark-ignition engine and every airframe powered by those engines.

All piston engines and aircraft are certified for G100UL.

There is now a legal alternative. Working as intended.

Edit, looks like there is an alternative https://news.ycombinator.com/item?id=38040091

It's already nearly choked to death by regulation, but that was a step too far.

But they also clearly have been working to mitigate it, and now that they have an alternate are banning leaded avgas and launching it.

So what is your rant about exactly?

If general aviation were to be banned, then as commercial pilots die off or retire, it would be difficult to hire new commercial pilots with as much experience as new commercial pilots have historically had.

Do you even see it in the list?

This NIH study shows it as ‘small, but significant’ - accounting for anywhere from 2.1-4.4% of the lead found in children’s blood near piston airports.

https://ehp.niehs.nih.gov/doi/10.1289/ehp.1003231

Less than 5% of the amount of lead total in their blood from that source, literally for the highest risk segment you can find. Even if completely eliminated, the other 95% isn’t going anywhere.

Even if you don’t average it out across the population, it’s hard to argue that isn’t so close to zero that nearly any significant benefit anywhere else would make it not a rush.

Most airborne lead pollution now is industrial anyway, and that is clearly the calculus there. As is the #1 and #2 sources of lead ingestion for children, old paint and old pipes.

I’m glad they’re getting rid of it, but I’m not going to complain they didn’t drop everything to rush it. Especially since if they did, they’d almost certainly kill more people in the resulting plane crashes.

* In the same category of human harm as nerve agents, dioxin, and methylmercury.

https://www.aopa.org/news-and-media/all-news/2021/july/27/ga...

https://www.epa.gov/archive/epa/aboutepa/epa-takes-final-ste...

Now they're going to ban leaded avgas, which should force the for adoption, since there IS now an approved general purpose alternative.

It'd be especially useful if they could run on regular jet fuel, then turboprops/jets and pistons could use the same fuel infra.

Diamond Aircraft have had success selling planes with diesel engines recently, and even started a subsidiary company to manufacture them: https://en.wikipedia.org/wiki/Austro_Engine

In the early days of aviation (like 1930's or such) there was some effort to introduce diesels for long-range aircraft, the idea being that the heavier powerplant would be offset by the lower required fuel load due to better fuel economy. But they weren't successful.

More recently there has been something of a renewed interest in aviation diesel engines, the motivation being they can run on Jet A-1 in addition to diesel fuel. Jet A-1 is what jet (and turboprop) aircraft use, and is available at basically every airport worldwide, is much cheaper than avgas, and no risk of being phased out like the leaded avgas being discussed in this article.

Now that there is an unleaded alternative, older planes will slowly replace their engines at the next engine rebuild. There is a grave pilot shortage already and the FAA loathes to make GA even more inaccessible than it already is so it’ll be a slow process.

It is fully compatible with existing engines https://www.g100ul.com/

>Will I have to modify my engine or aircraft to use G100UL avgas?

>Other than placards, no modifications are required. A small placard is attached to the engine and "stick-on" placards are applied to refueling ports. In addition, there is a short POH supplement added to the AFMS.

The engine change is shit pushed by the leaded-gas manufacturing lobby.

Lol, inaccessible? Y'all don't even need airstrips to take on and off, for Part 103 ultralights technically not even a license. Meanwhile, here in Germany, first pay up thousands of euros for the ultralight cert, and you have to use dedicated airstrips instead of your farm's field. Oh and if you want to get beyond ultralight, do everything from scratch for the PPL, no credit/transfers.

There's going to have to be a concerted effort to fix type certificates and fuel distribution all at the same time. A slow effort is going to be more problematic.

G100L is approved for all piston aircraft [1]. The only reason someone couldn't buy from them would be obstinacy.

[1] https://www.aopa.org/news-and-media/all-news/2022/september/...

You still have to go here (https://stc.g100ul.com/aircraft/) and buy paperwork that makes your individual airframe and engine legal. What the FAA approved was for GAMI to sell that paperwork for all piston aircraft.

[I am seriously curious; on the one hand, owning and flying a small plane is an expensive, privileged hobby which tends towards the lower-upper-class demographic, but it also requires complying with a shit-ton of government regulation and direction already.]

An alternative exists, but the FAA needs to certify it for each aircraft type. The majority of aircraft types are not certified for this. No A&P is going to do this because the plane won't be legal to fly in most cases.

And at the risk of editorializing, I've never seen the FAA do anything with the goal to making GA more accessible, at least not intentionally.

They have. It's done. nobody needs to worry about liability for switching. Availability will be a short-term problem, and banning leaded fuel will get it fixed quickly.

https://www.g100ul.com/

People just can't see the end result of their ideologies.

> It is a fuel additive, first being mixed with gasoline beginning in the 1920s as a patented octane rating booster that allowed engine compression to be raised substantially. This in turn increased vehicle performance and fuel economy.

"The Man Who Accidentally Killed The Most People In History"

https://www.youtube.com/watch?v=IV3dnLzthDA

These things are possible without lead as well, it just costs more money to do so.

You can dump as much fuel in the cylinder as you want (in fact, most airplane operating handbooks call for a very rich mixture on takeoff because of the cooling effect).

People have been looking for alternatives for a long time, but it's difficult because leaded aviation gasoline is not a very large market, and there are substantial regulatory obstacles.

But adding high-octane gas to a normal engine doesn't make it go any more boom, in fact, it goes less boom because it doesn't burn as much when it booms.

Modern engines can be designed to advance or retard timing based on knock, so they can run on different octanes and provide different power curves.

And that's exactly where i was wrong :-)

I was a professional mechanic around that time, and I had coworkers that thought that not only would high-octane gas give more power, would also swear it increased fuel mileage. Neither is true. High-octane fuel has less energy per gallon than lower octane fuel, it can’t give better mileage. (Now, “mechanic” != “engineer”, but c’mon, guys.)

[0] Yes, Captain Pedantic, I’m aware of knock sensors and computerized ignition timing. It was a quarter century ago.

This stuff started to show up in the late 1970's-- the 1981 280ZX Turbo my dad had was equipped with a knock sensor and would retard timing and add fuel.

By the mid-90's this was relatively common.

On many modern cars, high octane gas gives you more boom. They are designed for high octane gas, but the engine management computer is able to detect low octane gas and prevent damage from predetonation-- giving up some power.

>They are designed for high octane gas The vast majority of modern engines are designed for 87 octane, and not downrated to 87 octane, because that would give you poorer performance than a clean sheet 87 octane design, and single digit percentages matter here.

There's a whole lot of cars that say "Use premium fuel only" with compression ratios of >10.5:1, but rely upon anti-knock sensors to retard timing (and adjust mixture) to avoid detonation with 87 octane fuel.

More or less, if you want to build a light weight/high power engine you want a higher compression ratio. As the piston travels upward on the compression stroke higher pressures are achieved and this allows designers to take advantage of different crank/cylinder characteristics to make more power in a smaller, lighter package.

We used lead in car gas because engine timing technology and fuel delivery technology were analog/mechanical and really very limited in terms of tuning potential. The cheap hack was just to use a fuel that was more resistant to burning in the first place. Just add a hotter spark/ignition system and it was good to go design wise. Given the old tech running in most GA planes, this was a natural thing to do at the time and the problem was well understood. To point here, modern non-lead additives have been around for a long time and the problem can be adequately solved with a non-lead substitute.

If you wanna get deep with this, take your old normally aspirated car and bolt a turbo on it!

(In comparison, it was well-known at the time that ethanol can also increase octane, and it wasn't protected by patents.)

Lets look at numbers as of today:

Cesna 172 - 75kw engine, on 50kw power makes 1000km as 200km/hr. Engine plus fuel weight 350kg. The engine costs $26K.

Today's lithium batteries like ones used by Tesla is 280wh/kg. At retail similar batteries cost $400/kwh.

So, we can have 75kw electric engine and 100kwh battery at the same weight as ICE engine plus fuel on Cesna 172 and at a retail cost of $50K and have 2 hr flight of 400km. That isn't a worse starting point than what Tesla had 15 years ago against ICE cars.

If your fuel meets ASTM D 910, it contains lead. If it doesn't contain lead, it doesn't meet ASTM D 910 and therefore definitionally isn't 100LL, so if your engine type certificate data sheet calls for 100LL, it unavoidably calls for lead.

If you are flying an aircraft that is thus-certified, flying it with a different fuel is, per the FAA definition in 14CFR3.5, flying an unairworthy airplane.

"Airworthy means the aircraft conforms to its type design and is in a condition for safe operation."

That's the legal reasoning that the Gami STC is required: to change the TCDS of the engine and airframe to permit a fuel other than 100LL and still be considered airworthy. (The STC process is totally workable and, IMO, doesn't need to be "fixed" and Gami has basically done the work you're asking to be done AFAICT.)

That’s what the STC process does legally, just being done by the engine/airframe manufacturer instead of third party (presumably because they wanted to continue selling engines/airframes).

Don't forget that aviation engines are require a lot of regular rebuilds. In a car you wait until something breaks, in an airplane you replace parts long before they might fail to ensure it doesn't break when in the air. So for many we can just add replace the seats/valves in the next tear down and be okay.

[1] https://www.aopa.org/news-and-media/all-news/2022/september/...

IMHO, it'd be much better to have an explicitly adversarial and separately-funded dual-track system at such agencies, similar to how the justice system works.

E.g. FAA-Innovation (responsible only for their goal) makes their strongest case and presents research on why unleaded gas should be adopted ASAP. FAA-Safety (responsible only for their goal) makes their strongest case on why no change should be made.

All arguments and facts are published in public. Then higher-level decision makers arbitrate and make a call.

The root of all evil is that from a career perspective, "defer and take no action" is always safer for individuals in positions of regulatory authority. Worst case, something that's always been wrong explodes, and you blame it on the last person.

In the current blended safety+innovation system, it's too easy to obfuscate intentional inaction in endless "more study is needed" bullshit.

The exemption for leaded fuel in GA should have expired a long time ago. It's ridiculous that the FAA was allowed to keep punting this issue essentially forever, and the only reason a transition is happening now is because they finally decided to take responsibility for it, rather than because there was any legal requirement for it.

GA flying is important for a lot of industry, and a lot of remote communities. it might have taken some work, but they could have found a way to use unleaded fuel in airplanes in fewer than 50 years.

Having written this, it almost seems like too obvious of an idea to even post about...

For example, before they figured out how to sell and onboard SMBs, there was at least three teams working on solving that problem while I was there, including mine.

Once there was a “winner”, that team would get more funding (aka budget) and the people on the other teams tended to be absorbed into the winning team or would be repurposed onto other projects.

This wasn’t a codified, explicit operating system, but basically is how they worked for awhile (but I’m unsure how it works now.) The gist was to hire smart people and let them figure it out.

https://www.g100ul.com/faq.html#testing

Clearly it isn't okay to harm someone without their knowledge or consent.

(yes in some other countries)

If there is a conspiracy I suspect it's the government exerts a light hand on things rich people do.

What surprises me is the refineries didn't tell the light aviation industry they weren't going to make leaded gas anymore. If they'd done that the Feds would have kicked them some cash to develop an unleaded version.

Aero engines run at a substantial fraction of their rated power output basically full time[0].

The fact that auto engines can be run on unleaded, lower octane gas at 10,000' or more doesn't really tell us that the same low octane unleaded gas is suitable for an aero application.

[0] And in some cases are rated for more power for limited lengths of time such as takeoff. See here, for example https://medium.com/s/story/the-long-way-round-the-plane-that...

You can just add lead to unleaded gas (which was legal until 1996 in the US), so even if you could convince them to be altruistic in this way others could just work around it.

About 11 thousand barrels of 100ll are produced every day in the US. Compare that to 4.9 million barrels of diesel daily, and you can see why it is a bigger priority. In this case 100ll is a literal drop in the bucket.

But also its a rich guy hobby that generally isn't very visible.

Hospitals. Nuclear power plants. Airports. Laboratories.

With engine failures in aircraft however, the consequences can be way more dire - particularly in GA where it's (at least in the US) even being allowed to fly without a license at all (Part 103 ultralights), and forget about regular legit simulator training on what to do in that case.

Take your total load (10MW) divide by 5 (2MW) and you need 5 2MW generators, buy 7 and run 6/7 and your "down for yearly maintenance" generator can be offline while your "oh shit we installed the wrong fuel filter and the injectors clogged" generator also fails.

Much harder in a plane.

Those regulations don't apply to 1. existing installations in trucks or 2. generators.

> the FAA has a statutory mandate to prescribe standards for the composition or chemical or physical properties of an aircraft fuel or fuel additive to control or eliminate aircraft emissions which the EPA has found endanger public health or welfare under section 231(a) of the Clean Air Act. In issuing these final findings, the EPA is making such a finding for emissions of lead from engines in covered aircraft.

Power tools run much better on it because it contains no ethanol.

My portable generator starts much more easily after sitting for a few months if I use AVGAS instead of what I buy at the pump. It's because the ethanol gums up the carbonator.

Are you telling me all these aircraft that fly over my house are filling the air with lead?

How much environmental lead contamination are we talking here?

This was true up until last year, when G100UL was approved as a drop-in replacement for 100LL. It does require a STC and the associated paperwork, but this is apparently pro forma and quite cheap, and doesn't require any modification to the aircraft apart from some placards. The problem, of course, is that G100UL isn't really available anywhere yet, while 100LL is still ubiquitous.

Until recently this was true. But since September 2022, G100UL is legal and certified for "every spark ignition piston engine and every airframe using a spark ignition piston engine in the FAA’s Type Certificate database.”

While I'm rambling, the dual spark in a GA engine is really interesting.

Not a rhetorical question, I am genuinely curious.

New designs must work with leaded fuel since that is the fuel which is available - until avgas contains no lead this will continue to be the case.

Side note, most new planes are sold without an ecu.

Jets (and turbo-props) run on kerosene basically.

The lead is an additive that acts as a lubricant and older engines aren't certified to run without it.

That's going to be bigger twins and prop planes like the Pilatus