The End of Leaded Avgas, GAMI's G100UL, and the EAGLE Plan to Get the Lead Out of General Aviation by Twenty Thirty

Leaded aviation fuel is on its way out. Following a 2022 EPA endangerment finding that lead from piston aircraft harms public health, the FAA and industry launched the EAGLE program - Eliminate Aviation Gasoline Lead Emissions - with a goal of removing lead from general aviation fuel by the end of 2030, without grounding the fleet. Two unleaded fuels are competing to replace 100LL: GAMI’s already-approved G100UL and standards-based fuels like those from Swift Fuels.

Why General Aviation Still Burns Leaded Fuel

Here is a fact that surprises most people: general aviation is the single largest source of lead emissions into the air over the United States. Not factories, not smelters - piston airplanes burning fuel out of the pump.

The fuel most piston pilots use is 100 Low Lead, marked 100LL on the pump. Despite the word “low,” it still contains tetraethyl lead, an additive that has been in aviation gasoline for generations.

Lead does one job exceptionally well: it boosts octane. That lets a high-compression engine pull significant power without the fuel detonating - the destructive pre-ignition that can damage a piston at full throttle on a hot day.

The problem is the other thing lead does. It is a neurotoxin, with no safe blood level, particularly for children. Automotive gasoline had its lead removed decades ago. Aviation never did, because there was no drop-in replacement that could keep a big-bore engine from detonating on takeoff.

What the EPA Finding and EAGLE Program Mean

In the fall of 2022, the Environmental Protection Agency issued an endangerment finding for lead emissions from piston aircraft. In plain terms, the EPA formally determined that lead from aircraft exhaust endangers public health.

That finding is the legal trigger. Once the government determines something endangers public health, the regulatory machinery starts turning - and it does not turn backward.

Rather than simply banning the fuel and grounding a large share of the fleet overnight, the FAA and industry stood up EAGLE (Eliminate Aviation Gasoline Lead Emissions). Its goal is specific: get lead out of general aviation fuel by the end of 2030, safely, and without grounding the fleet.

Both halves of that goal matter. A transition that strands airplanes on the ramp - or worse, causes engine failures in flight - is a transition nobody wants.

The Two Roads to Unleaded Avgas

There are essentially two paths to unleaded avgas, and they are moving at very different speeds.

G100UL: Approved Now, Rolling Out Slowly

The first path belongs to one company: General Aviation Modifications Incorporated (GAMI), a small outfit in Ada, Oklahoma, best known for GAMIjectors. Two of its principals, George Braly and Tim Roehl, spent roughly two decades developing an unleaded 100-octane fuel that works in every piston airplane.

Their fuel is called G100UL. Instead of pursuing a new industry standard through a committee, GAMI used the Supplemental Type Certificate (STC) route - the same FAA approval pathway used for new props and avionics.

In 2022, the FAA cleared the G100UL STC for essentially the entire fleet of spark-ignition piston aircraft and engines - every airframe, every engine. If you buy the STC, you can legally burn G100UL today with no engine modification and no new tank - just a placard by the filler.

But approval and availability are two different problems. G100UL has been slow to reach the ramp. Questions and disputes have been raised about how the fuel interacts with certain paints, sealants, and hoses over the long term. GAMI says those concerns are overblown and being addressed, but some in the distribution chain have been cautious. The approval is real; the rollout is a grind.

Swift Fuels and the Standards-Based Path

The second path is the industry-standards road, driven by the major engine and fuel companies. It aims to qualify a fuel that any refiner can make to a published specification and move through the existing pipeline exactly like 100LL.

The best-known candidate comes from Swift Fuels, which already sells UL94, a lower-octane unleaded product that runs well in low-compression engines - trainers and older aircraft that never needed 100 octane. Swift and others are working toward a 100-octane unleaded fuel that clears the whole fleet through the standards process.

The tension between these two roads is the story: one is approved now but rolling out slowly; the other flows cleanly through the existing system but hasn’t yet crossed the finish line for the high-octane, whole-fleet solution. EAGLE is officially keeping both paths alive, because betting the entire fleet on one horse is the worst possible outcome.

Why This Matters for Pilots

If you own an airplane, watch the STC and your local field. Availability, not approval, is the real constraint right now.

If you fly a low-compression engine - an O-200, a lower-compression O-320, and many classic trainers and taildraggers - you may already be a candidate for UL94 unleaded fuel, which can be cheaper and cleaner. Check your engine’s certification with your mechanic. Some pilots burn 100LL out of habit when their engine was never certified to need lead at all.

If you fly high-compression or turbocharged, you are the reason the 100-octane fight matters. Your engine genuinely needs that octane to avoid detonation on a hot, high-elevation climb. You cannot simply pour in a lower-octane fuel. For you, the answer is a full-fleet 100-octane unleaded - either the G100UL STC or the standards-based fuel behind it. Know which approval covers your airplane before putting anything new in the tank.

If you fly out of a small field, watch the supply chain. Some airports, particularly around parts of California, have already moved to restrict leaded fuel ahead of the national timeline. Santa Clara County shut off leaded fuel at two of its airports a few years ago, and pilots there learned firsthand what happens when the leaded pump goes dark before the unleaded supply chain is mature. Some scrambled. That is a preview of 2030 arriving early in one location.

What Pilots Should Do Now

1. Confirm what your engine is certified to burn. Pull your type certificate data sheet or ask your A&P - don’t rely on hangar talk. You may have more options than you think, or fewer.

2. Go to reliable sources. This topic generates more heat than a jug on an August takeoff. Trust the FAA’s EAGLE program materials, the STC holder’s own documentation, and your mechanic - not forum arguments.

3. Keep your engine healthy for the transition. There’s good news buried here: lead is also what fouls plugs, gums up valves, and forces aggressive ground leaning to keep plugs clean. A future without tetraethyl lead means cleaner combustion chambers, fewer fouled plugs, and longer intervals between costly valve work. The additive we’ve fought to preserve has been quietly costing us the whole time.

The Bottom Line

The destination is not in doubt - the lead is coming out, and the EPA finding settled that. What remains uncertain is the road, the timeline, and whether the supply chain reaches your field in time so that 2030 is a smooth handoff rather than a scramble. The question isn’t whether, but when and how cleanly.

Key Takeaways

• General aviation is the largest source of airborne lead in the U.S., and the 2022 EPA endangerment finding set the phase-out in motion.
• The FAA-industry EAGLE program aims to remove lead from avgas by the end of 2030 without grounding the fleet.
• GAMI’s G100UL is FAA-approved by STC for the entire spark-ignition piston fleet, but availability at the pump remains limited.
• Swift Fuels’ UL94 is available now for low-compression engines; a standards-based 100-octane unleaded fuel is still in development.
• Pilots should verify their engine’s fuel certification now, rely on official sources, and expect cleaner-running engines once lead is gone.