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What is Avgas?
According to the chemical encyclopedia of Chemeurope.com, aviation gasoline – or avgas for short – is a fuel used in piston-engine and Wankel engine aircraft. It is different from standard gas because it uses tetra-ethyl lead, or TEL, to enhance combustion. The low volatility of aviation gas is important for aircraft engines, which regularly operate at high altitudes and have high temperature engines.
Many people confuse jet fuel with aviation gasoline, but they are in no way similar. Jet fuel is similar to kerosene and is used by large commercial and military aircraft.
Avgas is identified by two numbers. The first is the “aviation lean” octane rating and the second is the “aviation rich” rating. The aviation lean rating is much like the anti-knock index for vehicle grade gas. Aviation rich is the rating supercharged engine conditions using an extremely rich fuel mixture combined with elevated temperatures and high manifold pressure.
- 100LL – This grade of aviation fuel has a lower lead percentage than 100/130. Almost all piston aviation engines use 100LL, but it will soon be phased out because of high levels of toxic lead.
- 82UL – Similar to automobile gas, this aviation gasoline is used in aircraft that have an octane rating of 82 or less or an anti-knock index of 87 or less.
- Avgas 80/87 – Because of its low octane rating, it can only be used in low compression ratio engines. It contains the least amount of lead of any aviation fuel.
- Avgas 100/130 – This higher octane grade aviation gas contains a high percentage of lead, which is why 100LL was designed as a replacement.
Avgas Color Codes
Because different aircraft require different avgas grades, aviation gases are color coded with dyes to prevent fueling mishaps.
- 100LL – Blue
- 82UL – Purple
- Avgas 80/87 – Red
- Avgas 100/130 – Green
For more information about Avgas, its grades, and other regulations visit these helpful sites:
Shelf Life: According to an EAA article, the shelf life of aviation gasoline is about one year under optimal conditions. The main points of concern when storing avgas longer than one year are oxidation and gum. Gummy fuel can seriously hamper the performance of aircraft engines, causing decreased power and possible engine failure over time.
Storage Tips: Because it is essentially motor gas with combustion stabilizers added, avgas can be stored in standard aboveground storage tanks (ASTs) or underground storage tanks (USTs).
- Store avgas in a cool, dry area away from direct sunlight and excessive heat.
- Avgas shelf life may be increased by using a nitrogen blanket.
- Tanks must be impact, fire, and ballistics rated.
- Check tanks regularly for imperfections, leakages, or any other damage that may impair dispensation or safety.
- Regularly test fuel for moisture and remove it immediately.
Although USTs have long been the norm for aviation gasoline storage, many smaller and private air strips are moving towards AST usage. ASTs are more cost effective to install; easier to test, check, and repair; and allow faster detection of leakages or other malfunctions.