San Diego Airport, One Million Gallons of Leaded Avgas, and the Unleaded Alternative Nobody Is Using

San Diego International Airport sold more than one million gallons of leaded 100LL over a two-year period - making it the top airport in the country for leaded avgas volume. An FAA-approved unleaded alternative was available at the same facility the entire time. The gap between available and chosen is now a data point in a policy argument that goes well beyond fuel chemistry.

Why San Diego’s Avgas Numbers Matter

Lindbergh Field sits in the middle of one of the largest metro areas on the West Coast. It handles regional jets, turboprops, and piston traffic, surrounded by a dense residential population that watches aviation’s environmental footprint closely.

That context is what makes the volume figure significant. According to AVweb, the leaded fuel sales at this single airport represent the highest volume in the nation. At an airport this visible, in a regulatory environment this active, those numbers don’t stay quietly in a fuel log.

Where the Unleaded Transition Actually Stands

The FAA launched the EAGLE initiative - Eliminate Aviation Gasoline Lead Emissions - in 2022, with a stated goal of deploying a fleet-wide unleaded solution by 2030. Two approved alternatives exist today, and they are not equal in scope.

Swift Fuels UL94 works well for lower-compression engines but does not cover the full general aviation fleet. GAMI’s G100UL received a fleet-wide Supplemental Type Certificate from the FAA in 2022 - a meaningful milestone. It carries the same octane rating as 100LL, requires no engine modification, and covers the vast majority of certified piston engines. The certification problem, for most operators, is already solved.

The problem is distribution. G100UL is not at every FBO. Getting unleaded fuel into a reliable supply chain requires infrastructure investment, long-term contracts, and time. San Diego has it. Pilots there are still choosing leaded by an enormous margin.

Why Pilots Keep Choosing 100LL

100LL’s lead content isn’t incidental. It acts as both an anti-knock compound and a valve lubricant, enabling high-compression engines to run at full power without detonation. That’s real engineering value that pilots and operators understand from decades of experience.

Beyond the chemistry, several practical factors keep 100LL as the default:

Habit. 100LL has been the standard answer for so long that switching requires a deliberate choice, not just availability.

Uncertainty about compatibility. Even with a fleet-wide STC, individual operators often have questions: Is my specific engine on the approved list? Does my POH need a supplement? What does my insurance say? Those questions create friction.

Cost. Unleaded avgas has generally priced higher than 100LL at many locations. For flight schools and high-utilization operators running tight margins, fuel price differentials matter.

Perceived risk asymmetry. If a Continental or Lycoming has run on 100LL for twenty years without issue, switching to a new formulation requires extending trust to a certification process some operators haven’t fully tested themselves.

The Regulatory Risk Pilots Should Understand

San Diego’s lead emissions are under active scrutiny. The Environmental Protection Agency has studied lead emissions from piston aircraft for years. Local advocacy groups have pushed for restrictions on piston operations near residential areas, with fuel lead content central to that argument.

When the top-volume leaded avgas airport in the country also has an unleaded alternative on the ramp, that contrast becomes a usable data point in policy arguments. And those arguments, if they gain enough traction, don’t end with a conversation about fuel preference - they can end with operational restrictions on the aircraft themselves.

This has happened. Airports facing sustained community pressure have seen constraints imposed on operations, not just fuel. For pilots who fly into metro-area airports, the fuel transition has a direct connection to long-term access.

What Pilots Can Do Now

Verify your aircraft’s eligibility under the GAMI G100UL STC. The FAA’s fleet-wide certificate covers the majority of certified piston engines that have been running on 100LL. For most operators, the paperwork path is clearer than it was before 2022.

Ask your FBO what unleaded options they carry. If pilots don’t request unleaded by name, operators have no business case to stock it. Consistent demand changes the supply equation.

If you operate a flight school or rental fleet, consider a volume commitment. FBOs make stocking decisions based on throughput guarantees. A training organization that commits to running volume through unleaded fuel is a fundamentally different conversation than a single owner asking politely.

San Diego as a National Indicator

San Diego isn’t anomalous - it’s visible. Most airports don’t track and publish leaded versus unleaded volume at this level of detail. The numbers surfacing there are a snapshot of a national reality: leaded avgas remains the dominant piston fuel, by a wide margin, even where alternatives exist.

The FAA’s 2030 goal carries real institutional weight. The question is whether the transition happens on the industry’s schedule - orderly, operator-driven, based on informed choices - or whether external pressure from regulators and communities forces a faster, less predictable shift. San Diego just put a very specific number on that question.

Key Takeaways

San Diego International sold more than one million gallons of leaded 100LL over two years, the highest volume of any airport in the country, while an unleaded alternative was available on-site.
GAMI G100UL holds an FAA fleet-wide STC issued in 2022, covering the majority of certified piston engines with no modification required.
The fuel choice is not just environmental - it is a factor in the political case for piston aircraft access at metro-area airports.
Pilot habits, compatibility uncertainty, cost, and risk perception all contribute to slow unleaded adoption despite available certification.
The FAA’s EAGLE initiative targets a fleet-wide unleaded solution by 2030; whether the transition is industry-led or regulation-driven depends heavily on operator choices made now.