Avgas 100LL is a high-performance aviation gasoline specifically formulated for spark-ignition, piston-engine aircraft. It is the most widely used Avgas grade worldwide, supporting a broad range of general aviation aircraft, including training planes, business aircraft, and specialized utility aircraft.
The designation “100LL” signifies:
- 100: Octane rating (Lean mixture rating of 100; rich rating of 130)
- LL: Low Lead content compared to legacy grades such as Avgas 100/130
Despite the “low lead” label, Avgas 100LL still contains tetraethyl lead (TEL) to meet the anti-knock requirements of high-compression aircraft engines, ensuring safe operation under high power settings, variable altitudes, and temperature extremes.
Refining & Manufacturing Process
Avgas 100LL is produced using extremely tight refinery control and quality assurance processes that exceed those of automotive gasoline.
1. Selection of Light Hydrocarbon Streams: Produced from straight-run naphtha, reformate, and isomerized streams. Components are selected for high octane potential, low olefin content, and excellent volatility control.
2. Precise Blending & Distillation Control: Strict boiling range of approximately 30°C to 170°C, with balanced vapor pressure to prevent vapor lock at altitude and ensure reliable cold starts.
3. Tetraethyl Lead (TEL) Addition: TEL added at controlled levels (≤ 0.56 g of lead per liter maximum per specification). Provides knock resistance, valve seat protection, and engine durability under high load.
4. Final Polishing & Filtration: Removal of sulfur, olefins, oxygenates, and trace metals ensures fuel is clean, stable, and deposit-resistant.
Key Characteristics (Expanded Explanation)
High Octane Rating (100/130): Prevents detonation (engine knock) and allows engines to operate safely at high manifold pressure. Essential for turbocharged and high-compression piston engines.
Low Lead Content (Relative): Lower TEL than older Avgas grades (e.g., 100/130), which reduces spark plug fouling, exhaust valve deposits, and maintenance frequency.
Excellent Volatility: Controlled vapor pressure ensures easy engine start-up, smooth throttle response, and reliable operation across altitude changes.
High Chemical Stability: Resistant to oxidation and gum formation, maintains performance during extended storage, and prevents fuel system contamination.
Typical Physical & Chemical Properties
| Property | Typical Value | Aviation Importance |
|---|---|---|
| Fuel Type | Aviation gasoline | Piston-engine compatibility |
| Octane Rating | 100 (Lean) / 130 (Rich) | Anti-knock performance |
| Lead Content | ≤ 0.56 g/L | Required engine protection |
| Density @ 15°C | ~0.68–0.72 kg/L | Accurate fuel calculations |
| Distillation Range | ~30°C – 170°C | Controlled volatility |
| Vapor Pressure | Controlled (per spec) | Prevents vapor lock |
| Sulfur Content | Very low | Clean combustion |
| Aromatic Content | Limited | Engine material compatibility |
| Color | Blue | Grade identification |
| Appearance | Clear, bright | Purity indicator |
| Net Heat of Combustion | ~43 MJ/kg | Energy efficiency |
Storage, Handling & Safety Considerations
Storage Requirements: Stored in dedicated aviation gasoline tanks. Tanks must be clean, dry, grounded, and protected from water contamination.
Handling Precautions: Highly flammable (lower flash point than jet fuel). Requires strict grounding and bonding during transfer. Must not be mixed with automotive gasoline (MOGAS).
Applications of Avgas 100LL
Primary Uses: General aviation piston-engine aircraft, flight training aircraft, business and utility aircraft, and agricultural aviation (crop dusters).
Specialized Uses: Vintage and classic aircraft engines, and engines requiring lead for valve seat protection.
Environmental & Regulatory Considerations
Contains lead and is subject to increasing environmental scrutiny. Many aviation authorities are working toward unleaded Avgas alternatives, but it currently remains essential due to global fleet compatibility, safety, and performance requirements.
Regulatory & Quality Standards
- ASTM D910 – Standard Specification for Aviation Gasolines
- DEF STAN 91-90 – UK aviation gasoline standard
- ICAO Aviation Fuel Specifications
- Note: Only fuel meeting all specification limits is approved for aircraft use.
Avgas 100LL vs Automotive Gasoline (MOGAS)
| Parameter | Avgas 100LL | Automotive Gasoline |
|---|---|---|
| Octane Rating | 100/130 | 87–98 |
| Lead Content | Yes (Low Lead) | Unleaded |
| Vapor Pressure | Aviation-controlled | Seasonal |
| Ethanol Content | None | Often blended |
| Altitude Performance | Excellent | Poor |
| Certification | Aircraft-approved | Not approved |
Advantages of Avgas 100LL
- Proven safety record in aviation
- Superior knock resistance
- Reliable altitude and temperature performance
- Long storage stability
- Global availability at GA airports